If you have a humanoid character, and have had a skin texture on it, have you looked at it, and wondered, “Why does the skin look flat?”
If that your question, then here’s the answer:
This is quite a common knowledge in painting world, but it seems that not a lot of people talk about it in 3D world.
In short, the leg has a tendency to have a cooler and darker color (purplish) than the torso, which has a warmer and lighter (yellowish/orangish) color.
The scientific reason for this has to do with something called myoglobin, a kind of protein in our body that binds oxygen and iron. In a muscle group that is used a lot constantly, they would require more oxygen and iron to power up that sustained usage.
Do you know which muscle group in us (or in chicken 
) that is used more than any other? Well, you’ve guessed it, it is the legs.
Anyway, I hope this helps.
Best,
Vincentius