Hair color, dyes and tints do not affect the test because they contain chemicals, not minerals, but it’s best to wash the hair at least once after applying a tint, dye or color rinse before cutting a hair sample.
Bleach, highlights and perms can alter the structure of the hair. So either sample the hair before a treatment or after you have washed the hair five or more times following a lightening, bleaching or perming treatment. The hair tends to re-balance after five washings. Since highlights are done on the surface of the hair, you can simply sample a piece of hair that has not been highlighted on the underside of your head.