should i get a table AC unit to cool room for night temp by 15 degrees?

Apart from being expensive and not guaranteed to work, it will not do anything that will make your buds any more special than they already are. If it does work, your leaves will turn purplish, but not your buds, which get trimmed off anyhow, so what is the point? To get purple buds you have to grow a strain that has a genetic dominance for this trait, like Pakistan Chitral Kush. Save your money, you won't get ant rewards bud wise from running an air conditioner....... You could try, but I doubt you will achieve what you are hoping to. If you do try, it is only during the last half of flowering that the LEAVES go purplish. P.S. - who cares about GOTM, it is all about helping people or offering opinions, not getting rewards.

High, 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. You do not want to use the techniques that you mentioned in your question. This will ony slow down growth and causing unnecessarily problems. Happy Growing! 😋

No. Do not

it would be a negative effect on growth... the biology in the plant while its cold as well as the loss of photosynthesis in the leaves as it starts to reflect portions of blue and red wavelengths (what colors we see is not being absorbed) -- those are the primary wavelengths of PAR. purple buds happen due to genetics. like mouse said, this will only change leave coloation -- like how fall/autumn colors come about you only need 68F or lower at night for this to potentially occur... some variation of course..

I was going to say something similar to m0use here... it's a massive waste of money so unless you've got money to burn, I wouldn't bother! I also understand that it's not just a matter of dropping your temps 15 degrees... the "magic" temp is around 62F. If you're growing a naturally purple strain, the color WILL come no matter the temp... Good luck

Either of those should work. Make sure you find out how much the temperature drops once you turn your lights out so you can have a good guesstimate on what you'll need to set your AC. Good luck.