when to start night temp control to get purple colour on plant/bud

dropping the temperatures will induce a color change by killing chlorophyll in the plant, the most efficient engine turning light into something usable. if you are asking questions about this, you might consider not doing it.

@TeesTrees disregard the previous answer as other factors can turn plants purple than genetics alone potassium deficiencies can do it as can very cold temps which it seems is the way you are thinking of inducing colours into your plant. However not all plants will exhibit purpling in lower temps so its a bit of a hit and miss experiment on your behalf in all honesty I would concentrate on achieving the best yield you can get from the plants rather than attempting a colour change .

High bro, As i mentioned in your earlier question. Genetics make your plant go purple, please look at my Blue Hash diarie. I did not do anything to make her purple it is genetics. When you want a purple plant or red buds you need to search for the right genetics. If you are interested in this you can search for the strain, Red Hot Cookies form Sweet Seeds or Purple Bud from White Label (I grew this one myself and it is a delicious berry tasting Indica strain). Happy Growing! 😋

You don't have to do this really get the tent fans x 2 filters and twin fan controller first before anything else learn the basics and then u can play around with making the plants purple and I'd try to get photos instead of autos I never get big yealds of autos max 1oz a plants and that's with no stunted growth cos your autos going to flower soon and there's not much you can do to stop it im afraid