Grown-out highlights may be trendy, but single process re-growth isn't because it looks too severe. Color your roots at home every four weeks (even if you have salon highlights). "Only apply [color] to the half-inch of new growth, Root Touch-Up by Nice and Easy has just enough product in the box to color through your part and around your hairline," Backe says.

Whether you've colored your hair at home before or not -- read the directions carefully. "If the box says run the color through the ends for five minutes, don't do it for longer. Your ends could wind up two shades darker than your roots because they are more porous," Pemouli� says. And we all know the trend is the opposite -- dark roots with light ends. As Whitney Port of "The City" proves here.

Paintbrushes and plastic bowls from beauty supply stores will help you get the most precise application. So opt for using those over the provided bottles and gloves.

If your color comes out too dark, head to the kitchen. "Dishwashing detergent is strong enough to remove some of that color," Pemouli� says. Wash your hair two to three times with it to soften the hue. She also discourages adding another color on top of the shade because "color doesn't lift color" -- so try to fix the problem by washing.