It would be nice, and might work in a pinch, but coloring white clay is not as simple as it seems.
Polymer Clay Information and Tutorials - The Blue Bottle Tree
Sanding and Buffing Polymer Clay - The Blue Bottle Tree
Kato Polyclay – KatoPolyclay
12 Polymer Clay Myths - The Blue Bottle Tree
The Right Way to Use Polymer Clay - The Blue Bottle Tree
Plaques Can Be a Design Feature - The Blue Bottle Tree
Storing polymer clay mixes the easy way - The Blue Bottle Tree
Review of Cernit Polymer Clay - The Blue Bottle Tree
Do you apply mica powder before or after baking polymer clay? - The Blue Bottle Tree
Storing polymer clay mixes the easy way - The Blue Bottle Tree
Beginner Roadmap - The Blue Bottle Tree
Baking Polymer Clay - The Blue Bottle Tree
Plaques Can Be a Design Feature - The Blue Bottle Tree
13 Things You Should Know about Polymer Clay - JSThreads