Not a bad debut…

Your primer is just the right amount. Easy enough for the novice but not too verbose.

It’s worth noting (though I understand this was published by Sketch) that these blend modes are not limited to Sketch. The standard set comes from the ancient dark ages of computer graphics and are ingrained in pretty much any self-respecting imaging application.

The idea, of course, stretches back further to photo processing techniques. (Y’know with like… chemicals and physics!)