Brassiness can be dealt with by using a toning color product or through the use of special purple shampoo. In terms of hair care, "brassiness" refers to unwanted warm red, orange or yellow tones in hair, and this is typically a problem in hair that is meant to be a cool blond, white or gray color. Toner uses a strong chemical process to alter the warm tone down to a cooler tone, and purple shampoo is a milder product that is said to produce the same results as toner.
Many people with light hair, whether it is an all-over blonde or highlighting on darker hair, prefer that their hair tone is closer to a cool yellow or white than a reddish or orangish color. This is why "brassiness" is often discussed as a problem related to hair color.
Toner products work in a similar way to hair bleach, helping to push the lightened hair further into lightness. Purple shampoo is a bit easier on the hair and is also simpler to use; it can be substituted for normal shampoo and used on a regular basis for those people who want to avoid brassy color. Because purple is yellow's contrasting color, the addition of this purple pigment helps to cool down the look of blonde hair.