I've tried them all and like them all. I prefer red mainly for the following reasons:
1) red's the same color as my Aimpoints and illuminated variables...I'm a creature of habit.
2) red provides plenty of contrast in any venue. At night, bright isn't necessarily better in ambient light when trying to focus your dilated pupil on a target <100m. It's all about contrast. Any weaponlight is gonna blacken out your ACOG reticle anyway. Beyond that - aim your red, green, yellow, blue, or purple ACOG reticle into a sodium street light - and it's gonna fade on you. Not washout, but fade. The washout arguement is a weak one. In the rare event it does happen, disconnect the ACOG and employ that $250 pair of BUIS holding down your upper.
3) red is bright enough during the day as it is....I don't know about you all, but I find that I have to cover a portion of my TA11 just to prevent the bloomin' when taking an aimed shot. Those 11's are bright! There's a lot of fiber optic tube riding atop that scope.
4) I forget what 4 was
5) the human eye is reportedly more sensitive to green....lol, I don't know....a bright red reticle against most natural backgrounds just seems to stand out better for me than the green. Up close when running around with both eyes open, I have yet to find a venue where the red donut didn't stand out bold n' bright. I will admit I find amber a better fit for my hunting rifles. I don't think the amber is as "obstructing" as my red. I want to put my reticle on the target, not my target behind the reticle. That's where the speed is.
I don't think you can go wrong with any color. They are ALL bright under ambient light. Just pick what you want and roll with it. Not saying I don't like the green. I find it quite sexy. I just think the red is more practical. YMMV, of course ... hence Trijicon's incredible line up of products. One of my favorite company's out there.
I also think any discussion about red vs green vs amber is really spillting hairs. Go get yourself an ACOG already and shoot the shit out of it!