Any strain can be changed color. Some is in the genetics like purps and such. But if you want to turn a non purp to very purple drop the temperature to sixty for the last week and a half of flowering, I assure you the stem, part of the colas or flower will turn dep purple. Basically you are slightly stressing the plant, by doing this it will produce more resin glands as the plant thinks winter is coming so it produces the glands to protect itself. The color changing is also from the slight stress given in the end. It doesn't make it a purple strain just because it has purple in it. I just think it gives it more appeal in the mason jars.