Step 5: Coloring Oogoo
About the equivalent of 5 or 6 drops of oil paint per teaspoon of silicone will result in solid colors. I mix the color well with the silicone before adding the corn starch.
While you can leave it white, it is a good idea to add some color to make it easy to see if you have a well mixed batch. Adding color does not appear to significantly effect the hardness or flexibility of the final result.