I prefer the Meprolights green/green myself. I've tried a couple of different brands and styles but always go back to the Mepros. The dots are a little bigger (which is easier for me to see) and clearer than other's I've tried. The Trijicon's are clear but the dots are too small for me. I've also tried the TruGlo night sights which I really didn't like. The dots where not clear, too small (looked more like just white dots) and the front dot was way off center in the front site post.
So now every one of my carry guns has the green/green Mepros installed on them.
I have Meprolights Rear:Green 2 Dot, Front:Green 1 Dot on my Glock 27. I have Trijicon Rear:Green 2 Dot, Front:Green 1 Dot on my Glock 22. I had Glock Factory NS Rear:Green 2 Dot, Front:Green 1 Dot on my Glock 26.
IMO the Meprolights are larger dots and wayyy brighter. As for the color it doesn't really matter, but I would like to check out the different color front than rear version.
Meps are what Glocks use as their factory offering. Hard to go wrong. I recently used a discount code on the Ameriglo site and put their sights on my two Sigs. Very nice sights. And, they were relatively cheap.