Impossible color

I’m surprised the section towards them end about alternating high contrast colors producing impossible colors doesn’t link to “fechner colors” [0]. I am red-green colorblind, but when I was young I would stare at my dark ceiling fan spinning over the white ceiling and see very vivid greens and purples swimming across the blades. [0]: https://en.m.wikipedia.org/wiki/Fechner_color

Back when I was a wee art student, I had a phenomenal printmaking professor who was an expert in inks. One of her projects was a monotype, and mine included a cloud background, but I couldn't get the colors right: a dusky yellow cloud background. You've probably seen the hue following an afternoon thunderstorm late spring. I'd mix, and mix and end up with a dark yellow, that when printed over blue turned green, or reddish or some other stupid…

I've used this as an example of (non)-vector spaces in a linear algebra class before. Light perception is based off the stimulation of three color cones, so three (positive) values. The light available to us stimulates those cones in certain ways and three light colors are enough to form a "basis" of the space of perceived colors. But the fact that the values are always non-negative means that there are possible cone-stimulation values that are never achievable by our light…

> No physical object can have an imaginary color. It's weird that this extremely logical conclusion is built up by borrowing two very crucial cultural words, fictitious and imaginary, as labels for a definition. I wish they would pick other labels than those. Why? Because if someone who doesn't know the difference says "are there imaginary colors?" You end up having to answer "yes" and be wrong, or "no" and be wrong. Yes: There are imaginary colors, and there's an…