HELP! Leaves for one plant very dark purple/black.

[don2020]

I am over 5-months into a coco-noir grow, each plant 1 week apart, with the one on the right/black leaf one planted about 7-10 days prior to the one on the left/green coloured. I am not far from harvest and I've been running it on Red wavelength light for a few weeks, so I hadn't noticed the change of colour until today. I needed to change the pre-filter on the carbon filter due to the lingering smell outside of the grow tent, and discovered the entire plant, except for the buds, which are a lovely green, is black/dark purple.
Any idea if there's something I can do, or should I just pull it and harvest it asap?
The one on the left has some yellowing and purple leaves, I am less concerned about it because it looks fine, but this is my first grow and any advice for that would be tops as well.

[Catfish22]

Looks genetic, plants are like humans the same genes don't cross every time.
Nature only uses part of these genes each time but different sets each seed.
Apparently one of one of these phenotypes in your strain has purple coloring. I would say grow it out for sure and post back so we can see if it "outgrows" it!

Cooler temps can cause the color to come out, also. What are your dark and light temps running?

[JoshuaGrowin]

Beautiful colour with some serious frost, congrats!

[SoOrbudgal]

I think i outah come over and help you harvest them lovely gals.

[PLreef]

I agree with Catfish22 . I get packs of seeds from breeders and depending on strain some grow green and some grow purple. No big deal. Treat it like normal.