If you use high quality products (shampoos and conditioners) specifically designed for colored hair, your hair color should last from 4 to 8 weeks, with 5 to 6 being typical. That's a big range, but the variance has to do with your tolerance for fading, how often you wash your hair, how hot the water is and how much you're in the sun. It's a sad but true fact that reds don't last as long. Color works by depositing molecules of pigment in your hair shaft and no matter what you do, they eventually come out. Water is the main culprit, but if you use inexpensive shampoos with detergents, your hair color will only last one to three weeks. A cheap non-color safe shampoo can strip red in one washing. You may think we're saying that in order to get you to buy the better stuff here, but the higher detergent drugstore type shampoos will truly strip your color quickly. Also, conditioners with a high parrafin content will bind to your color and make it wash out more quickly.