Mix 1 oz. of food coloring with a pint of warm water and 1 tsp. of sugar. Stir until the sugar is dissolved.
Pour 3 inches of the solution in a vase.
Place your cut carnations into the vase.
Wait while the dye moves up the stems. This could take one to 24 hours. Your carnations will absorb colored water through their stems, transporting it to their petals through capillary action.
Rinse the stems and make a fresh cut once the petals have turned blue. Place the carnations in regular water.