Hair Color Casting After RelaxerQ: Is there any way to prevent color casting after a relaxer?
A: If you are referring to the tendency of a relaxer to slightly alter the tint or hue of the haircolor, then the only real solution is to perform color services only after the relaxer service in order to ensure true and accurate color results.
The chemicals used in both thio and hydroxide based relaxers and straighteners can alter the hair's color by as much as two levels in many cases.
If however, you are referring to a situation where - after a relaxer service - the hair develops a particular color cast, you might try using a moisture rich conditioner to help smooth and seal the cuticle layer of the hair and make it less penetrable and therefore less likely to be susceptible to color alteration.
How to color hair
Hair straightening and relaxers Q&A
Using relaxer and hair color at the same time
Is it possible to get my hair dyed and straightened in one appointment?