deriv LSK ETT STT aSTA ALPH OLDHOMEPAGE NEWHOMEPAGE
Even though /pANini does not bother to say so, if anyone or anything has purple hair you can call him / her / it a purplehair.
You can compound this way any two nouns when the first describes the second. No sUtra is needed to allow this sort of compounds. These are /bahuvrIhi. Some English examples —
threehead
copperhair
barefoot
twoleg
scarface
horseface
basketnail
In English most of these are allowed only when they are nicknames, like "Scarface". In Sanskrit however they are always allowed, to the point that you may say azvamukhaH अश्वमुखः "horseface" whden you mean "he has a horse(horselike) face" or "the guy with the horse face".