More to explore:
frosting by numbers x
Icing colour chart #2
Frost by Numbers: How to Make Frosting Colors
All these colors were achieved with red (r), yellow (y), blue (b), and green (g) food coloring mixed into white frosting. The amount of drops needed for the color you want is underneath the icing color.
Frost by Numbers: How to Make all Colors for frosting
How to make frosting colors with a regular box of food coloring: How awesome is this chart. I want the last one
DIY Cupcake Frosting