An arctic blonde goes brassy. Washed out highlights look flat and white. Roots get so hot you run for the fire extinguisher. To avoid these color calamities, follow these four level rules. 

1. Identify the Natural Level
It may sound simple: to follow the three-level rule, you have to know the client's natural level. But that born-with-it color isn't always as obvious as you think. "Don't assume you can read your own levels without using a swatch for comparison," says Haircolor Expert James Jordan. "Use a swatch book, and be sure to hold the swatch in the…