If there is no technical/game code reason and it's just another area they chose not to flesh out I'm bummed. There is no excuse to use 'realism' as a way to not include their Aliens/Mermaids into a feature. That ship sailed once you made the occult in the first place.
Also I don't understand calling picking the colors logistically impossible. It might take a few drafts to see what looked nice but the tones are all blue/green/purple. Pretty easy colors to have darkened and effected by red and the white tone would be the one, to me, with the most debate. Does it go darker pure grey? Do we tone it grey blue when tanned? Ect. I took art in school too and would have never gotten my degree if I told them I couldn't conceptualize tans on blue.
As for the light thing yes, black is absense and white is all colors. The reason it seems different with paint is its because how light reflects off the objects we see. For example an object appears blue because it absorbs light from all sides of the spectrum except blue which is reflects back at us. A black object absorbs all colors and reflects nothing back. The black "light" so to speak we perceive is the absence of all colors. But it's caused by the object or paint absorbing all colors. That's why when we layer pigment it gets darker so we think of it as having more colors but what we're really getting back from light is less.
The paint gets greedy :>
