Returning to blonde is a lengthy process that involves removing as much of the red dye as possible, bleaching the hair and using toner to obtain a neutral blonde shade. The process usually cannot be completed in one salon visit.
Going from red to blonde is a difficult coloring job because red is such a dark color. The first step is to minimize the red as much as possible. This can be accomplished with a hair color correction product made to strip dye, available at most beauty stores. Another approach is to let the dye fade naturally on its own. Red dye tends to do this relatively quickly. A deep cleansing shampoo, used regularly, can help the process along.
The hair will then need to be bleached to remove the remaining red. Bleaching removes color effectively but is also damaging to the hair, so it should only be attempted if the hair is healthy. Bleaching can be done at home, although considering the potential for irreversible damage, it is best to go to a professional colorist for bleaching. Blue bleaching products usually give better results than white ones when eliminating red dye.
After bleaching, a toner should be applied. Toning adds a purple or blue-tinted base color to neutralize any brassy or orange tones, which may remain after the bleaching. Toning may be the last step for some people if the resulting color is acceptable. Alternatively, a colorist can over-dye with blonde dye or highlights.