Thinking about colors [Part 2 of 2]
In Part 1, I covered topics that I thought were more generally useful to researchers — i.e., how to choose the colors you use. Here in Part 2, I will discuss color from more technical and psychological approaches.
First, a disclaimer: Part 1 was oriented about giving advice on selecting colors for figures, Part 2 is more about understanding colors a bit more deeply and considerations you might want to keep in mind. This is definitely not ‘required reading’ as a follow-up to Part 1.
Color Spaces
In grade school, you probably learned that the primary colors are red, yellow, and blue (RYB). However, when making digital graphics, these are often done by defining colors either as RGB (red-green-blue) or CMYK (cyan-magenta-yellow-black). RGB is based on additive colors, where adding all of the colors produces white — this is how light works, and how colors shown on a computer monitor would be defined. In contrast, CMYK is based on subtractive colors, where adding all the colors produces black — based on how ink/paint work, and how colors are produced by your printer.
So, where did RYB come from? In school, you would be using a ‘paint’-like medium to make your colors, but kids don’t really learn about cyan and magenta early on, so these colors are instead called blue and red. (See http://sciencequestionswithsurprisinganswers.org/2015/01/22/why-are-red-yellow-and-blue-the-primary-colors-in-painting-but-computer-screens-use-red-green-and-blue/.)
Depending on what you want to do, RGB and CMYK might be all you need to know about color spaces. But, if you’re more interested in how color vision works in humans, you may want to use LAB color space instead (well, L*a*b*…but that’s more nuance than I want to get into here). LAB still has three components, but instead they correspond to luminance (L*), red-green (a*), and blue-yellow (b*).
As you might know, this is more analgous to how cones in the human retina work, and LAB space can be used to represent all human percievable colors, which isn’t true of RGB or CMYK.
So, if you study color vision, or want to match picture stimuli for luminance, you should be using LAB color space (vs. mean RGB values). In fact, linear changes in RGB space result in exponential changes in luminance (see https://en.wikipedia.org/wiki/Gamma_correction).
Color Names
Now that we have a better understanding of how we can thinking about different color spaces and how human color vision works, let’s think about how we name colors.
It is interesting to consider that human color vision sensitivity is not evenly spaced across the spectrum and is likely biased to detecting colors related to blood oxygen saturation (see http://rsbl.royalsocietypublishing.org/content/2/2/217.short). From this, think if you were to try and name colors — you will end up having more colors in the red spectra (pink, red, purple), whereas you likely have less color names in the blue and green portions of the spectra. Awhile back, xkcd did a survey and asked people to name colors.
Others later took a more thorough approach and mapped out color names across the spectra more comprehensively, and produced a great visualization.
Gender differences
From this xkcd comic (and perhaps also from anecdotal experience), it is also apparent that men and women use color names a bit differently. This same xkcd comic also provided a great source of data to map out these differences, and see what names are more/less likey to be used by either gender.
Cultural differences
Another interesting consideration is cultural differences in color names across cultures. I know less about this topic and is an open-debate in the literature, but think it’s an interesting consideration. Here’s the summary of one view point:
Berlin and Kay also found that, in languages with fewer than the maximum eleven color categories, the colors followed a specific evolutionary pattern. This pattern is as follows:
All languages contain terms for black and white.
If a language contains three terms, then it contains a term for red.
If a language contains four terms, then it contains a term for either green or yellow (but not both).
If a language contains five terms, then it contains terms for both green and yellow.
If a language contains six terms, then it contains a term for blue.
If a language contains seven terms, then it contains a term for brown.
If a language contains eight or more terms, then it contains terms for purple, pink, orange, and/or gray.
That’s all for my current thoughts on color — hope it was interesting to read!
