Having eyes as old as the rest of me is a disadvantage. It also encourages both research and practical experimentation. The advice you are about to receive is based on olde pharte eyes, so adjust as necessary.
Yes, green is the easiest to see, but be careful of how much you put out there at the far end of the barrel. Those great big green glowing balls are nice, but they can overwhelm both your eyes and your ability to see everything that is going on beyond them. Test to see if you run into the situation or not.
As for what to put at the back end? Orange costs more than yellow, but shows up better. Red in small size can either not show up or look too blurry. The best theoretical setup I have seen is a green dot out front and an orange dot in the back - stack then up green on top of orange sort of like the Heinie Straight-Eight, but literally green resting on the top of orange instead of the gap for the rear sight notch.
Hope this helped.
stay safe.