How can I adjust the spectrum of color for my skin tones in my game?

Normally I agree that I find the diversity refreshing, but the darker skin tones do not look real to me. I have a lot of black friends and they look nothing like this at all. I didn't want to come across offensive, my first language is not English and I had no other way to express what I wanted. I guess what I am trying to say is that I am looking for a way to adjust the spectrum of color in my skin tones that is more realistic for what is in real life.