Hey, Sismicious here.
I've worked on hair colors recently. Indeed, we first thought about a color randomization system, but there was a big problem : working this way only allows to darken and lighten every base color the same way. The more neutral way to do this is to use black and white and then lower their opacity.
But by doing so, we have dirty and ugly colors, whereas setting our own colors for everything is of course perfect to achieve beautiful color harmonies and blending.
As you can see, the difference is very noticeable. And even in this study case, I adjusted the opacity values to make it look acceptable, but the same values will have a different render on another base color, and we can't control that.
Finally, randomization creates strange color mixes, which are not always beautiful. And everyone knows girls like to be pretty, even if they're brothel slaves, right?
We also choose to cut the hair in 4-5 parts, depending on the angle. That's quite a lot for animation! But we're aiming for the best quality we can produce right now, so why not?
I hope this first "official" article was interesting for you! If you have questions, please drop me a comment on this post.