One of the most common problems that people encounter when dying hair brown is unwanted tonal qualities. If the wrong color is selected at the outset, the results could be disastrous. Applying ash or cool colors to blond hair in an effort to dye it brown often results in a greenish cast or undertone to the hair. This is because brown hair possesses near equal parts of all three primary colors: red, yellow and blue. Blond hair has no red pigment whatsoever. If a cool color with a green or blue base is applied, the result is blue, green or blue-green hair. Fortunately, fixing this type of color error is easy to do.