OK SOoo! I use genesis heat paint for Painting my Babies.
Why, Because if I make a mistake I can easily wipe it out, and I do not have to paint in a rush. Seriously this has been a good invention for us artist, because it only dries if you apply enough heat to it making the artist control his/her own work.
Something you should really consider using is a color wheel
This wheel helps me with everything from my choice of colors for clothing to my eyeshadow, to my house colors and for my little babies. If you are not familiarized with doll reborning, this wheel is very useful. A slight blue coating is used for reborning dolls (for beginning), but why is that you might ask. Well my friend this is, because your doll will have a peachy color and what is on the other side of peachy color, yup you guess it your blues.This will naturalize your colors. In this case peach and blue giving your baby a more natural look.
That's where I got the idea for using this wheel on polymer clay babies too.