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

I would not focus on trying to make it go purple for a few reasons. number 1 is its a massive waste of energy to install ac just to make it turn colours. number 2 is that only the fan leaves and some tips of the buds will turn purple, does not penetrate into the nuggets. number 3, its only a week old. and this is something that gets done in the last few weeks of the plant, if its getting cold every night from a sprout to harvest it will have stunted growth as the purpleing is caused by chlorophyll breakdown and that's need to grow your plants nice and big. It would be a much better investment into your time and pocketbook to just get a strain that is naturally purple/red. The idea of using the AC units that runs off of ice is also not ideal. They create an influx of humidity in the air and when you in late flower you do not want extra humidity unless your below 40% RH ambient. Good Luck! ***disclaimer, multiple people are answering all questions as there is a contest called GOTM, when a user is selected as the answer they get a point. Please see the contest page for information regarding the details: growdiaries.com/giveaways/GotM-August-2022 Please note, when you reply to anything on the questions part of Growdiaries website, no one will be notified of this. Not even if you use a "@" tag in their name. Best to reach out to them in DM using your inbox, it can be found in the bottom right hand corner of the site. It's the small paper airplane button, it will be highlighted green if you have new messages***

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.