I have my red as my 40 yd pin. it fades the fastest, so if i can't see the red pin I better not shoot as there may be a twig ect in the way that i also can't see. Green is my 20 yd. If they are inside of 20 yards and my green is still glowing I should be ok to shoot. I've also noticed that by looking at my watch the green pin fades almost exactly at the end of shooting time (1/2 hr after sunset) of course its a little off on cloudy days.