If you color your hair before taking a hair folicle test will it affect the results of the hair test

If it is an ETG hair test, then you can dye/bleach, use intense shampooing or even go swimming 2-3 times a week to reduce or eliminate EtG from hair. However, for FAEE marker, washout is not possible. To your defense, it may be alcohol from hairspray, gel, cosmetic products that may cause false positives. Again, the cut off value is not supported in any literature and is a topic for debate, however the law may consider the same cut off value that the lab used.