i see that it looks like you want to get the "purps", some strians have this gene bred into them. kinda like a flower there are different colors. but most strains will turn purple with low temps. much lower than 65 degrees. basically the plant needs to get almost to the point of freezing, it has something to do with the horemones and the root system. i have heard of people using large blocks of ice in theer resevoirs, but this is not recomended. mainly because it WILL stunt the growth. many times this is a mistake that will effect the yield if it is toyed with by an inexperienced grower.

strains such as purple urkel and purple haze will turn purple with little effort, just a slightly lower tepm than usual with the lights on or off, but if you have one of these strains, you need to make sure you do not pull too soon. many times the purple color you are looking for will develop fully during the last 2 weeks of flowering and even durring the drying proccess. actuallly it is a common mistake to pull your crop too soon by a week or two since most growers are impacient stoners...guilty