DIY Color Booster for Brunettes: Whip 1/2 cup cocoa powder, 1/2 cup plain yogurt, 1 teaspoon honey, and 1 teaspoon apple-cider vinegar into a paste. Shampoo hair, squeeze out the water, and apply the mask. Keep it on for 2 to 3 minutes. Drape a towel around your neck to prevent the mask from dripping, as it may stain skin temporarily. Rinse, then style as usual.