"To color the cream, mix food coloring in with a rubber spatula until the cream is uniformly colored. Amounts will vary and will be based on the brand of food coloring and how light or dark you want the cream to be. I recommend food coloring gel, available in small tubes, because it’s less watery and easier to work with. Start with a few drops and add more as you mix. If you are making a dark color, like black, the cream can become loose or watery in which case you should mix in some extra powdered sugar until the texture resembles shaving cream. For white decorator’s buttercream, or to dirty-ice a cake (Carlos-speak for applying a crumb coat) before applying fondant, you do not need to add any color." - Buddy