i think its pretty well accepted that all cannabis plants will go purple under the right circumstances. The 'right circumstances' are actually bad conditions - like cold weather.
The purple is a secondary photosynthesis system used as back up if the more efficient green chlorophyll system fails. What we consider purple strains, are basically the retarded ones which lose their chlorophyll much quicker than other strains, i.e more sensitive to sub optimal conditions, or simply shorter lived chlorophyl. That is why purple strains are only really favored by people interested in looks - like me.
Even if a purple plant is amazingly strong and high yielding, it would always have been better if it was green.
Hi! I understand what you are saying and thats why I wrote the pheno I have has purple buds no matter the temp.
Just the calyxs are purple right from the start of flowering, and they go from light pruple to dark as they mature, the leaves remain green.
So this is a purely genetic trade and it has nothing to do with the enviroment conditions, like cold temp.
I dont care much about the appearances, and I wouldnt keep it if it were a low potency or a very low yieldnig plant.
For me the priority are the psychoactive effects, and Im sure thats true for most of us cannabis friendly people.
But it sure looks nice, so thats just icing on the cake.
Sorry couldnt be of much help with the strain selection. But my point was that although what you are saying isnt wrong, there are exceptions. Cheers!