If your roots are showing and your next appointment with your colorist seems unbearably far away, try this tip from Gary Howse, a colorist and salon co-owner here in the Seattle area:
Before bed, rub a little color depositing shampoo into your roots and blow dry the area. When you get up in the morning, wash and style your hair as normal. Your roots will be stained with the pigment in the shampoo and won't be as noticeable.
If only everything were so easy!