If your hair is medium brown your stylist could use an ash blonde to get highlights, but they would not be platinum..they would still be in the golden tones...In order to lighten medium brown hair several levels, a forty volume developer must be used. (Ecocolors Developers have flax and castor oils in them).Your stylist could purchase these colors. Have your stylist contact us for more details. This technique of lightening the hair several levels should not be attempted at home because highlighting takes experience technically and artistically to achieve pleasing results.
