If you mean the shades. I mix the typical fleshtones with pink and violet. It gives the pig more pinkish color. I am using spanish colors, mostly Andrea and Scale75 colors, if nothing, it will give you hint, what I mean.
For base layer I used 1:1 SC34 - Fuchsia and SC20 - Basic Flesh with some water
For lightnings I am using more and more light skin tones like or you can add white color as well.
For shadows I add just a little bit by bit more of SC56 - Violet. It will make deeper and deeper shadows.
There is need to use glazing/layering technique or wet blending to achieve good result. So after base layer is applied, I use only very thinned colors to make thin layers like "wolpertinger_press" said. I use combination of 1:1:1 for color:water:glaze medium(Vallejo brand), but its just what I like. You should really watch out, what you are doing, the previous layer has to be dry, or there is danger to erase that.
Even better color transition you can get with the wet blending, where you apply different color between previously applied color. But its quite advanced technique, you need to have some kind of color extender to slower drying and have quite good experience with mixing colors, to get the correct color to model's part in-time.
You can see my entry for Iron Painter 2016. I painted Gracie.
Hope this helps a bit.