hows and whys of rainbow hair coloration: how to dye your hair like an engineer

Not the philosophical hows and whys, of course, but the procedural ones. This radiant violet mane ain’t natural; I consumed many hours of DIY hair blogs to distill my current repository of cumulative knowledge about how to properly fry your hair. I’ve re-purpled myself often enough that it’s now a relatively casual and painless process, but for the uninitiated, I’m decompiling it out of my head here so you need not replicate the effort of navigating the conflicting and varied opinions of the blogosphere.

me super saiyan transforming into my favorite yarn skein

All the blogs I could find only gave procedural advice specific to the exact hair color/texture on their head, which was massively infuriating. As usual, my tragic flaw was my overwhelming compulsion to un-silo knowledge and underlying principles at cost of sleeping or eating, so I was determined to compile enough generalized information so that more people could not only figure out what steps they needed to take to get the colorful results they want on their hair, but also understand what’s happening at each step so that they can debug mid-process.

While you still have the potential to become a DIY hair horror story if you get impatient and try to instantaneously become platinum blonde in one sitting, you don't need to be afraid if you are willing to start slow, take more time to understand your hair, and maybe not achieve your perfect color on the very first try.

Caveat: I found little to no information about bleaching type 3 or 4 hair. If you have type 3/4 hair, a lot of this information will still be generally useful, but you may want to look up specific tips from fellow curly folks, start with a test streak, and proceed more cautiously, as types 3/4 are much more porous than types 1/2.

* As a general rule, I only do irreversible things once I have a fairly complete understanding of how they work. If you do not operate the same way, feel free to skip straight to Bleaching: How for the cut-and-dry instructions.

Hair salons will fill your ears with needless worries about DIYing it. Fear not; coloring your hair at home is actually pretty easy and averages around $4/month for lazy people like me, or a few bucks more if you like maintaining your roots and thus bleaching more often.
You’re not even saving time by paying to get your hair done since your body has to be present the whole time :)

Bleaching: Why

Like most physical pigmentation processes, hair coloration is subtractive, like mixing paint or coloring over markers with other markers. Thus why you need to bleach so light to dye unnatural colors, even if you want them to come out dark; purple over brown is basically dark brown. If you try to put an unnatural color like blue/green/purple over anything darker than light blonde, your color won’t show up well without direct sunlight.

Even if you’re already very light-haired, you’ll still want to bleach a little because porosity also helps with dye retention. Basically, if your hair strands are porous, dye can stick in there, and if your hair is super smooth and healthy, it’s more difficult for dye to deposit. Obviously, too much porosity is bad when your hair becomes so ragged it breaks off. (If your hair is naturally very porous, you will want to be more careful here.)

1. Bleach addresses both of these needs by simultaneously decolorizing and fucking up your hair. To apply it, you mix a bleaching powder with an oxidizing agent, called a developer. (Lest you should mistakenly think to substitute hydrogen peroxide, know that the maximum strength developer used on hair is only 12% hydrogen peroxide.) This is a surprisingly exothermic process which will be active for around an hour or until you wash it off. If you haven’t done this before, continuously check your bleached bits to see how light they’ve gotten, and err on the less-bleachy side until you figure out the right duration for your hair.

After bleaching, there are typically orangey-yellow (“brassy”) tones left behind. This is due to some combination of your natural keratin coloration and remaining hair pigment, and it’s another reason you must lift so much color to dye your hair rainbow. Your hair color isn’t turning into a lighter version of itself in HSV space; it’s more analogous to a change in RGB space.

In other words, bleaching dark brown hair doesn’t turn it into light brown hair — it removes a color component that was previously canceling out or concealing an orange color.

This is what over an hour of bleaching with 40 vol developer and foil gets me. *tiny guitar weeps*

Asian hair is particularly notorious for being a shocking orange underneath, and unfortunately, I can’t dye myself purple at this stage because purple plus orange makes brown. So even though I want to end up at a relatively dark shade of purple, I need to bleach myself all the way to blonde before the purple will be cleanly visible. If you want to end up at red, orange, or even green, you can take it a lot easier. For example, my friend with green hair gets there by bleaching to medium yellow and then applying turquoise over it. White will be the trickiest, with silver a close second.

A few approximations of applying dye over different base colors, obtained with a photoshop multiply layer and corrected by a decade or so of watching/helping my friends dye their hair funky colors.

The reason to wrap hair in foil while bleaching is that it retains heat and moisture, and heat accelerates oxidation. I don’t have citations for whether the moisture is also a critical factor because hair bloggers don’t write about reasons why things work, but I can empirically tell you that without foil, an hour of bleaching merely lightens my hair from black to darkest brown. At a minimum, I would guess the moisture helps with evenness via facilitation of particle mobility.

More later on timing.

Many of my colorfully-haired brethren are horrified by the amount of bleaching it takes to render me blonde. You caught me; my hair is actually a large wild animal which has made its nest upon my scalp.

Bleaching your hair will change its texture! Curly-haired internet people often report that bleaching straightens their hair. Personally, my natural hair is very straight and smooth, so it becomes wavy after bleaching because damaged hair has more texture (and, by corollary, volume) than super-smooth hair.

2. (optional) Double processing is when you follow up bleach with toner to go platinum blonde. Toner deposits violet which, when mixed with developer, counters light yellow and cancels to get hair that looks white. If you’re not on a quest to make your hair silver, white, or some super light pastel, you probably don’t need to worry about toner.

If you do want to have white/silver hair: don’t bother using toner until you are already as blonde as you can go. It’s subtle enough that it won’t really make a difference if you are still brassy yellow.

Bleaching: How


  • Bleaching powder: L’Oreal Quick Blue ($15 / 16 oz tub, or $5 / 1oz packet)
  • Developer: L’Oreal Oreor Creme Developer ($6–8 / 16oz)
  • Toner (optional): the Internet consensus seems to be Wella Color Charm — White Lady ($5 / 1.4oz)
  • Plastic cup+utensil to mix the bleach (metal will react with it)
  • Gloves, foil, shower cap, and a sacrificial T-shirt and towel
* I’m not specifically attached to these brands — they work great, but they’re just whatever was cheap with good ratings on Amazon.

Developer comes in different strengths (peroxide concentrations).
These are their recommended use cases:
10 volume - For very mild color lift, such as if you’re naturally light blonde.
20 volume - Standard prep for most hair.
30 volume - For darker hair that needs more color lift.
40 volume - For very thick black hair, a.k.a. mine. Will destroy fine hair.


The amount of time you need to bleach to get to blonde varies drastically by original color and hair thickness. My friends have reported ranges from 20–30 minutes for thin light hair to two hours for thick Asian hair (we gaze enviously upon the light-tressed who casually color their roots on a whim), so increment carefully and visually check often until you reach your desired result.

Personally, I’m completely okay with getting a slightly uneven result instead of bleaching all the way to a blank canvas. The remaining base color mutes the purple a little, and my goal is to look like my hair is just naturally purple (whatever that means).

I polled my colorfully-haired brethren to get more heuristics. While this is by no means a statistically meaningful sample, it might at least help provide a starting point if you have never done this before. I would recommend starting at the lowest point that applies to you and working your way up once you see the results.
Apologies for the relative lack of diversity; most everyone I know who does this has type I/IIa hair. (Straight hair has almost no styling options compared to curly hair and it gets boring after a couple decades, so we gotta make up for it somehow.)
East Asian
40 vol, 120 min
40 vol, 120 min
40 vol, 120 min
40 vol, 60 min
20 vol, 50 min
South Asian
40 vol, 100 min
Pacific Islander + Caucasian
30 vol, 80 min
South Asian + Caucasian
30 vol, 60 min
20 vol, <= 20 min
20 vol, 30 min
30 vol, 30 min
30 vol, 40 min
30 vol, 50 min
40 vol, <= 20 min
At the extreme end of the spectrum, I use 40 volume developer in two back-to-back hour-long sessions. This is not recommended except for the thickest, blackest hair, and even then you should start lower and work your way up to be sure. The first bleaching takes me from black to brownish-orange, and the second to banana yellow. If your hair is not black, you will almost definitely want to bleach for less than 50 minutes.

Once mixed with developer, bleach will continue oxidizing for about an hour. So if you need over an hour, you will actually have to do this in two separate sessions.

Internet wisdom claims that multiple bleaching sessions should be spaced by at least a week so your hair has time to “rest”. I don’t know what that means since hair is dead and has no intrinsic repair mechanisms, but maybe you’re supposed to use the time to apply external repair mechanisms, like protein treatments.

I currently do my two bleaching sessions on the same day because I’ve discovered my natural hair is crazy healthy, but I reached this conclusion through a year of cautious testing — I started out spacing my bleaches by a week and conditioning heavily with many protein treatments, then progressively decreased the spacing once I knew my hair hadn’t been too damaged. Start cautious! It’s easier to have funny-looking brassy hair for a week than to regrow all of your hair.

If you have reason to be extra nervous — if your hair is naturally porous, fine, or damaged — you can always start your hair journey by just bleaching one streak in an underlayer, and isolating the rest of your hair using a shower cap!

Addendum: When you redo your roots, minimize any overlap with the already-bleached parts of your hair. Underneath the dye, it is still as porous and blonde as when you last bleached it, so you don't want to damage it extra.

What to actually do

Don your designated bleach shirt and gloves. Mix the bleach and developer according to instructions on the packaging. Thoroughly massage the mixture through your hair, wrapping handfuls of it in foil as you go until you look like some kind of cyberpunk space medusa. If you have as much hair as me, it can take half an hour to get through all of it, so do some bilaterally symmetric pathfinding to avoid noticeable color differences.

If you don’t know how long to wait, continuously peek at your hair every 10 minutes to see what color it’s turned. Like bread fresh from the oven, it will continue to lighten just a tiny bit after you wash out the bleach, so it’s fine to err on the cautious side and wash earlier once you’re really close to your desired shade.

Once you have attained a satisfactory lightness, wash with shampoo and use an old towel you don’t care about. This is now your designated bleach towel because it will be totally ruined for anything else.

* Manually petting bleach downward with your fingers results in a relatively soft line. You will get a more obvious, harsh-edged growth line that necessitates frequent touch-ups if you use a brush applicator or bleach all the way down to your roots. Put bleach on your (gloved) fingers and grab semi-random chunks, then pull the bleach downward through the chunks.
* If you want, you can gradient your bleach instead of bleaching all the way down to the roots so that it looks more natural as it grows out. Since bleach is time sensitive, you can gradient by simply saving a few bleach-free inches on the first pass and then doing a second pass about 20 minutes before time is up. It also looks nice to variegate the bleach line with some highlights that go down to the roots.
(I no longer gradient, since I don't like the bleach boundary to show up brassy orange as my purple fades.)


Great — the hellscape of hair bleaching has run its foul course and your hair is now a horrible bird’s nest made of limp yellow straw. Now what?


1. Permanent dyeing is an oxidative process and must be used with developer, making it damaging to your hair. I don’t know much about permanent dyes except that they’re sort of analogous to bleaching and dyeing all together in one go. Many big brand name dyes, hair salon dyes, or drugstore box dyes will be this type.

2. Demi-permanent dye deposits color (on top of already-bleached hair) that tends to wash out in 2–8 weeks. Many of them double as conditioner, and are non-damaging meaning they’re not time-sensitive. All the rainbow-colored dyes I have personally used are non-damaging to leave in. Obviously, check first if you’re not sure.

Applying a non-damaging dye is way chiller than bleaching: put it on your hair, put that hair in a plastic bag, wait at least 30 minutes (I go for an hour, but you can wait longer for extra potency), and then take a cold shower until the water runs clear. Congratulations! You are now colorful and your hair has resumed a semblance of its former luscious glory!

freshly applied Special Effects Deep Purple

Brands I’ve tried
- Special Effects (fades aesthetically)
- Pravana ChromaSilk (extremely potent; bleeds on everything)
- Arctic Fox (doesn’t seem to bleed too much)
- La Riche Directions
- Manic Panic (fades quickly for me; YMMV)

Reputable brands I haven’t tried
- Goldwell
- Jerome Russell Punky Colour
- Joico

Some of these dyes at full strength (particularly Special Effects and Pravana) are so saturated with color that they continue to bleed out on your clothes and pillows for weeks. My friend who uses the same dye as me, but undiluted, was once asked if he had used his pillow to murder a Smurf. To mitigate such misunderstandings, mix with any cheap conditioner until the dye looks about twice as dark as the hair color you want to end up with — Pravana honestly looks the same if I dilute it to 1/4 or 1/3 strength. Bonus: you have now saved a multiplicative factor of money.

I currently use Pravana Violet diluted to 1/3 strength to achieve a blue-based purple, and touch it up every 3-4 weeks when the top of my head has faded. Cost comes out to $2–3 per application, since the underlayers fade slower and I don’t need to redo my entire head every time.
Undiluted, it lasts around 6 weeks on my friends (several of them started using my color recently, which is confusing for the rest of the world).
I used to use Special Effects Deep Purple diluted to 1/2 strength, which faded to bright magenta on me.
* Having trouble selecting your perfect color? Haircrazy is a great community resource on different dyes, with lots of photos of how dyes come out on different people's hair.
The streak is Directions Alpine Green. I’ve since switched to Arctic Fox Aquamarine to get a bluer turquoise.

p.s. Pastel dyes are a lie; they are merely diluted. Save your money and mix a small dollop of normal dye into cheap conditioner to get pastel.


Touching up your dye is far easier than re-bleaching, if you don’t mind roots — all you need is an hour or so of letting dye soak into your head (go read a book, and refrain from vigorously hugging anyone wearing white clothes) followed by a normal shower.

I touch up the faded top layers of my hair every 3–4 weeks, which is a pretty standard duration for most colors to stay vivid. Certain dyes can last for several months (I’m looking at you Special Effects magenta), while very delicate pastels may barely last two weeks.

Color composition and your base color factor into how your dye will fade. You're probably still a little yellow-toned underneath, so a faded blue will look green. When the blue component of purple fades, it leaves magenta behind. Remember that dye is subtractive and combining two complementary colors will cancel out to some shade of brown, so you can’t switch directly from green to red. I know some people who switch by rotating around the color wheel — like going from green to blue to purple to magenta to red.

If you do want to intentionally fade out your hair in order to dye it a completely different color, baby shampoo is supposed to be a good method.
DO NOT rebleach for the purpose of getting dye out. Only rebleach if you didn't bleach your base color light enough the first time, and your hair feels healthy enough to take it.

Things that will make your hair fade faster
- swimming
- hot showers
- shampoo
- sunlight/UV
- everything good in life so no use worrying about it

I've been in the no-shampoo camp for most of my life, which incidentally helps with color retention.


The dye should have helped make your hair feel less like someone tried to harvest straw from a forest fire, but it’s probably still less healthy than it was before you bleached the hell out of it.

Dainty Squid has gone around the whole rainbow of possibilities and writes some of the most thorough blog posts I’ve found about vibrant hair color maintenance; here’s her hair master post and color maintenance tips.

I am not the correct person to ask about aftercare. My hair is so strong that apparently even bleaching it with 40vol for two hours in a row and not owning conditioner couldn’t destroy it, so I don’t have much to say here except that I follow up each bleach+dye with a few days of Redken Extreme Anti-Snap Treatment and it seems to cancel out the post-bleaching limpness. My usual hair care routine is to wash it with plain water a few times a week, and maybe a dab of Dr. Bronner’s if I’m extra gross from camping or exercising.

Products my friends have recommended, the efficacy of which I can neither confirm nor deny: Bumble & Bumble hair oil, Pravana Chromasilk hair sealer, Olaplex, Aphogee protein treatment, coconut oil, argan oil, castor oil, shea butter, apple cider vinegar

Enjoy your new bond with strangers with the same color hair as you; nod wistfully at them, knowing you truly understand the sacrifices you made to get there.