CGI employed to complete the illusion that an actor has a different hue flowing in their circulatory system.
What do you mean by this? ...How flat and/or powdery make-up sometimes looks as it's caked on actors' faces, taking away skin's natural (if minimal) translucence?
Nah, it's something I harp about a lot, where the actors' red blood is visible in areas where makeup is impracticable or impossible, like the tongue or caruncles. The most hilariously obvious example is from, of all things, the one that $200 million to make, so clearly the technical ability was there--but there it is, huger than life on the theatre screen, Kid Spock's pink lip is bleeding green, and I'm at a loss to describe how that works.
I'd also like to see different races within a species. All the Cardassians are exactly the same shade of gray. The make-up may have changed throughout the seasons, but in each episode, every Cardassian is exactly the same color. Imagine one that's near black - not human "black" but actually near charcoal in color. Or one that's near white. And instead of the dark one having more rounded "African" like features, it be pinched and angular, and the lighter one be smoother and curvier. I like the idea of playing with norms. Why should alien races vary in the same ways human ones do?
I dunno. I've got nothing against morphological diversity in any given species (you know, like humans), but if they're going to do it, they need to think about how such diversity came to be in the environment of the particular alien.