You can tint WHITE CHOCOLATE, but there isn't a lot written about it. We use this technique with our Tie Dye High Hat Cupcakes.
You can “paint” colors on the set, molded white chocolate (or any chocolate) or white chocolate plastic — mix colors by combining powdered food coloring with cocoa butter in a 6 to 1 ratio (cocoa butter to food coloring) and keeping them warm while using them. (A yogurt maker is the perfect temperature range or keeping them in custard cups set on a heating pad set on low, low, low). Add the cocoa butter until you achieve a medium thickness in “paint”. Then, paint on your colors using a paintbrush. You can also silkscreen on the colors, if you have time!
However, paste food coloring, as powdered, can be used to color the molded white chocolate or white chocolate plastic with after you mix and refrigerate it for at least an hour. The chocolate plastic has to have the consistency of playdough. Knead the color in.
The best way to tint white chocolate while melting or already melted is with oil based coloring. But, you can safely use powdered food coloring. Do not use any water-based food coloring or the chocolate will seize and be ruined. Add the color slowly and stir, stir, stir while you do.
You can also use Merken's Candy Coatings. They come in a myriad of colors and all you do is melt them.
