In small bowls or mugs, combine the milk and food coloring to make desired colors. Set aside.
For each serving, use clean paint brushes or cotton swabs to "paint" a design onto the bread with the colored milk. Sprinkle with cinnamon sugar and toast in a preheated oven (350 degrees) or toaster oven until lightly browned.
For a no-cook version, substitute the milk with sweetened condensed milk and omit the cinnamon sugar.