In a glass canning jar with a top, place the granulated sugar and food coloring. Use 1 drop for light colors and 3 drops for bright colors. Note that some colors may need additional food coloring (black needs about 8 to 10 drops).
Shake the ingredients for about 30 seconds until the color is fully distributed. Add any additional drops of food coloring as needed; make sure to shake well to avoid clumps.
Pour the sugar onto a foil-lined baking sheet. Remove any clumps of food coloring with a spoon. Allow to dry for 20 minutes (or about 30 minutes for black).
Break up any clumps with your fingers, or shake the sugar again in the jar to remove the clumps. Use immediately or store in a sealed container.