What in this wonderful WORLD OF CANNABIS does not have mixed reviews, "its just nature to me baby"(in my austin powers voice), ice/cold is a part of their world, and thats what these complex plants are good at protecting themselves at a plant level to the point of turning hermie just to regenerate, so during the cold the cannabis senses its dying and try to put out all the resin it can in hopes of catching pollen for the last time, and the resin also helps to protect the plant, sorta like putting on a coat on, now on to the colors popping now not all plants will not turn purple but if its supposed to, it will turn with colder temps, and there other colors it will bring this out sorta like trees do in the fall, now there is a more scientific reason for this but easier to explain in laymens terms, but here you go if you want it the cold causes the chlorophyll at the time the most abundent chemical making the plant look green to disintegrate, and allow a couple other less abundent chemicals to show more carotene, and anthocyanin and these are the of colors yo see with relect whatever color they end up producing depending on the balance in the plant
P.S. My Days before Dark Plan Day1-Ice cold water. Day2-Let it sit. Day3-Water and Ice(to slowly melt and keep temps low for awhile. Day4-Let it sit. Day5-Ice only on soil. Day6-Dark Period 24-72 hours, and cut from bottom of stalk during dark for harvest day as this helps with drying and making sure all nutes or whatevers left that could affect taste is still in the roots, and not in the stems. Men this is for you "Kill her in her sleep MWUHAHAHAHAH"