The legend of green being a better color for sights comes from an article published way back in the 80's or maybe before in a prominent gun magazine. At the time people were experimenting with colored inserts inserted into the front ramp sights popular on holster guns. Some nerd, I wish I could remember who, said science proved humans pick up green better than other colors, I don't think it was valid for the application but a lot of people ran with it. I've also read that humans tend to see red as danger, fire and all that, green is safe a nice grassy spot maybe we looked for grass knolls back in the day. There are conditions where our eyes pick up differences in shades of green easier than others. I talked to a guy who was part of a team looking for inidvidual marijuana plants out in the wilderness from a helicopter once, thinking it would be damn near impossible, he explained that the difference in the green of that plant stuck out like it was neon,
TLDR I think green seems good partly because of the trick of the day effect, it's different than usual, can be brighter than red, we believe in some science project. For me I like red because I've spent a lot of time trying to find a red dot inside an old tube type electronic sight. Even on shotguns I prefer red. It's interesting that on one hand green shows up better has more contrast according the the green side, but then they sharpie their red sights so they aren't too bright.