From the Speedo site.
Chemical hair treatments + chlorine = trouble
After a colour treatment, tint, perm or highlights, your hair is at its most vulnerable. Try to avoid swimming for at least a week after chemical treatments in order for them to settle and prevent any chemical reactions or mishaps, like hair turning green, premature colour fade, dehydration or breakage. Ditto freshly applied hair extensions – leave them a few days to give the bonds and hair a chance to settle. Then, when you do hit the pool, soak the hair with tap water before you swim, apply a conditioning mask to the very ends, comb through and braid to protect from damage and tangles.