Changing Plant Colors

Lets say, hypothetically speaking, that someone had Trainwreck and Haze Mist plants. Trainwreck flowering and Haze Mist starting to flower, I was wondering if it was possible to add a little purple to the finished product. I've heard its possible through colder conditions, or nute mixes. Any comments or advise would be much appreciated.

no unless its genetically predisposed to being purple there is really no way

I've done some research online and to the best of my knowledge the Trainwreck can become purple and I'd think the haze could but I really dont know for sure. They would be grown with a 400 Watt HPS, Organic Soil