Place sugar in resealable plastic bag. Add 5 drops of food color for pale colors. Add more food color, a drop or two at a time, if more intense color is desired. Seal bag and knead gently until color is evenly distributed.
Spread in a thin layer on a baking sheet and break up any large lumps. Allow to dry thoroughly, about 15 to 20 minutes. Sift or press through sieve to return sugar to its original texture, if needed.
Sprinkle onto cookies or cakes before baking, or sprinkle onto cooled, freshly iced baked cookies or cakes.