I shoot with a Montana Black Gold sight. Extremely tough and lifetime warranty on pins. I also see green the best, with yellow fading about 5 minutes earlier, and red fades about 5 minutes before yellow.
I put my green pin at 20, red at 30, and yellow at 40. As long as I know the range and can still see my yellow pin I can shoot out to 40, if it is 30yards and I can' t see the red I could split the difference of the green/yellow and make a 30 yard shot (I would highly suggest practicing this a lot). If it starts to get really dark I wouldn' t want to take a shot over 20 yards anyway, so having my green 20 yard pin fade last makes the most sense.