I'm considering putting an optic on my Sig P365. I've only ever used irons before. There are red dot and green dot options for purchase, but don't know what I should choose. Do people with experience using both have any preferences between the two? Is it just a preference issue, or are there benefits for one versus the other? Thanks in advance.

Too many green trees and bushes around my area for a green dot.

I have several of each on pistols and rifles. Color really depends on how it is going to be used. I agree with the statement above. Hunting would be a little difficult with green. The red dots, in my opinion, are hard to acquire in brightly lit situations. Indoor, dimly lit range trips, it truly is a toss-up and up to personal preference. I would also think a person with astigmatism might have an easier time with green. I read places that the human eye more easily focuses on the color green as opposed to red. All that said, I have a Holosun Gold Dot on a CZ Scorpion Evo. I absolutely love it. That doesn't help you though, as it is made for a rifle.

No experience with green dots, but the one time I got to play with a red dot, I had bad vertical stringing. I was wearing glasses instead of contacts, and my rx is the sort to get prismatic effects at the margins - colors separate out. Blues refract towards the center, reds outboard. This isn't a problem with irons, but a holographic monochromatic red light source would shift depending on whether you look through the optic center or not.

This effect negates any positive value I might get from a red dot, but green shouldn't be affected as much. Of course, colorblind shooters may have different perspectives.