Asked Annalise Kiehn Score 4.6 votes Ways Make Your Dull Hair ShineClarify.Add oil.Use shine spray.Try supplements.Go easy with heat.Use humidifier.Other tips.Bottom line. Why does hair look dull after coloring Hard. Tone down hair color with vitamin C. - First, use one spoon to crush a few vitamin C tablets into small powder. - Mix with a little water to make a paste. - Apply the mixture on damp/wet hair (if you want to foam, you can add a little shampoo); use the comb to brush the mixture on your hair like a hair dye.