Stop coloring your hair immediately. Over-colored hair is already weak and porous, and dumping more chemicals on it causes more damage. Let it all hang out and go back to your natural color to give your hair a break.
Trim away damaged, broken hair. Sure it may leave your hair shorter than you're used to, but removing damaged strands will improve the look, and feel, of your over-colored hair.
Cut back to washing your hair once or twice a week. While the idea of infrequent washing may be hard to stomach, letting the natural oils from your scalp coat your hair protects it from damage. Use shampoo and conditioner especially made for color-treated hair, and cover your head with a shower cap if you must indulge in a daily shower.
Slap on a hair mask and relax! Hair masks are thick, protein-rich conditioners designed to restore softness and sheen to damaged hair. Apply a mask twice-weekly to damp hair, cover with a cap and let the mask soak in for at least an hour before rinsing with warm water.
Minimize heat styling over-colored hair, but if you absolutely must curl or straighten your hair, protect your hair with a leave-in conditioner. Rub the conditioner between your hands and run your fingers through your hair. Comb and style as usual.
It may be a scary thought, but chopping over-colored hair short is often easier than trying to fix over-colored locks. Starting over with fresh hair is much simpler than trying to fix damaged follicles.