My sister used to be a hairdresser, she recommended fairy liquid, tomato sauce or Head & Shoulders shampoo to strip the colour out a bit if you're in an emergency!
I must be weird.....I have never coloured my hair in my entire life! When they shampoo it at the hairdressers the girls always comment that it feels like children's hair. I'm dead lucky I guess as I only have to wash it about every three days, quick blow and ready to go!