Temperature will influence this factor if it's in the genetics. Lower night time temps of 10-15max lower then daytime temperature will accelerate this process called anthocyanin accumulation which causes anthocyanin to build up within plants. While chlorophyll is what gives weed and plants in general their green color, anthocyanin is what makes weed purple, and carotenoid is what will make weed yellow or gold. I'm late on your question but now you know. Cheers mate.