a lot of plants will turn puprpleish if left through a frost at the end of the season... what people dont realise is that this is not good for the buds... i read it in a Cannabis Culture Mag but cant find which exact one it was in to tell you exactly why... but go ahead and do it,, customers eat that shit up "ooooh purple buds,, they must kick-ass" ..... if you are selling the buds go right ahead but if its personal then dont