Wikipedia calls metallic colors colors, which implies that any arbitrary brdf is now a color. Personally I would only call the photons travelling through the air at any specific point in space a color, and say that the object’s color changes when you move it around. I guess you would still say that a red metal sphere is red though, so my definition doesn’t really work.

I was saying there are times when you can’t treat other colors as being made form primaries, specifically when the spectrum will later be separated. (by diffraction or by materials with a complex spectral response)

for example, you could have 2 clear yellow sheets that look identical when placed in front of a full spectrum white light. However, one lets through red and green and one lets through yellow wavelengths. Suddenly now they behave very differently when you put them in front of a green light - the one that only lets through yellow looks black and the one that lets through green looks green.

going back to the part where I labeled yellow as a slippery slope, its because we can’t really see whether there are yellow wavelengths or not in examples like these or others

also, a fun side note, you can actually see diffraction patterns by looking through any aperture (but a diffraction grating will make it more obvious) and these respond noticeably differently to all wavelengths and look wrong if you only consider the primaries. So, technically, if you’re looking at any scene through any sort of camera/lens system/eye, you can’t treat the scene as only having 3 primaries as it would look (imperceptibly) different if you considered all wavelengths. Actually, recreating this video in Python is what got me thinking about this. If you look at a very bright white point of light made of very specifically only red green and blue wavelengths you might actually be able to see this, it should look like

instead of

(its very subtle and you might need to zoom in but it looks a lot more noisy)

sometimes suddenly you can’t pretend color is just red green and blue, once you get diffraction or are using a spectral renderer or smth, but yea it works 99% of the time

I guess you could call this pink but I would normally think of it more in the magenta range of or

in the c/196 banner there is more red than green, meaning the fully saturated version wouldn’t correspond to a real wavelength

anyways, I’m not trying to say that those colors don’t exist because obviously we can see them, just that they show the weaknesses of human color perception

yea, if there is a single wavelength and its yellow we could see it. However, if you had a full spectrum of light and took away all of the yellow but added some red and green you wouldn’t be able to tell that there’s no yellow, because we can’t see yellow, only imply it from the red-ness and green-ness

i’m pretty sure you couldn’t pull off the same trick with red, green, or blue but I guess I don’t really know

I’ll start by saying the computer rgb and hsl models are an abstraction matching how we perceive light that doesn’t include any other spectral information that we can’t see

in terms of wavelengths of light, pink is not a hue, unlike other fully saturated colors it does not have a wavelength to go along with it

yes, you can combine red and blue to make pink, but then you’re looking at the wavelengths of red and blue and not those of pink (because pink doesn’t have a wavelength)

any color that isn’t red, green, or blue could be any one of an unlimited number of spectrums that would produce the same perceived result, but any fully saturated color other than pink does have one single wavelength that goes along with it

like I said above, hue is analogous to wavelength, saturation is analogous to the ‘unpure-ness’ of the wavelengths, and value/luminance is analogous to the quantity of those wavelengths - and pink is one that breaks this pattern

well these ones specifically are displayed on your monitor (which can only display red, green, and blue) so they actually aren’t real

your eyes are being tricked into thinking there’s yellow for example, when there’s really only red and green, this is because we can’t really see yellow, we can just guess that its there based on the relative red-ness and green-ness of the light

However, it is very lucky for monitor manufacturers that we’re so easily ‘fooled’

I guess the hue and maybe saturation are undefined there according to most color models (HSL would have hue and saturation undefined for white but HSV would only have hue undefined)

look at this chart, and look for the pink. It isn’t there, because pink isn’t real

I should have excluded king blue and violet tho, those are actually real, mb