I had read somewhere that you deprive potassium to get a purple, which would be fine for somthing like a sea of green with small plants, lacking nutes is recipie for lower yields, running a.c. during your dark hours 55' and below will turn water leaves and some seed pods on the strains like purple nepal or ppp. ... on the other side of that is heat, alot of your attic grows or outdoor greenhouses reach such high temps during the day that you will have no purple anywhere, if they are too high your plant will just stop growing all together, the whole purp. craze has some of my buddies running a.c. all the time, yeah it is real pretty and tastes gr8 but it is just another strain, I find that by switching brands after a half ounce you keep getting stoned to the bone, rather than smoking one strain only and not getting as high off the last doobie in the oz as you did with the 1st . you can die a carnation by using food coloring in the vase, I'm sure if you stuck a fresh stem in some red dye that some of it would make it to the bud and you could call it fireengine, or you might end up calling it compost cause that might not taste so good, if anyone is harvesting and tries some food coloring I'd like to hear about the results, tie-dye novelty buds