When picking images for portrait packs. The file "races.gd" (Strive>files>scripts>characters) is a really useful resource. You can check what hair, eye and skin colour each race spawns with.
However I'm not 100% on one thing. In that file, when a race doesn't have it's hair colour (etc) stated. Does it revert to a default range of colours? And what is that default range for each part?
My guess is blond, brown, black, auburn & red for hair. Pale, fair, olive, tan, brown & dark for skin. Blue, green, brown, grey, hazel and black for eyes.
If anyone knows for sure, that would be really helpful.