Given that the eye has about 1/8 the sensitivity to red as to green, for the same power green would be brighter.
I'll admit that red on green contrasts better the green on green, but the eye is also sensitive to movement. Move a bright green dot around and people will pick it out right away.
Well, he said the pointer he had was not able to be seen at the ranges he needed it to reach, and he as trying to get something that could reach the canopy heights. His 5 mw was only observable to 15 meters or less in his environment...which implies that its a visually crowded target area.
As even an el cheapo red pointer from Staples, etc, can make a dot you can often see ~ 50 meters away w/o a problem, 15 meters of useful range tells us that he has a tough target scenario, and needs more visibility than normal to see the dot.
If it were dark enough, sure, any color would stand out as a LIGHT. But, obviously, its daylight, and there's light filtering through the foliage that stops the pupils down, etc....and makes a teeny dot less noticeable.
A teeny dot that's the same color as the background I think would be just adding too much of a challenge.
So, while 532 is a nice color as far as visibility in of itself, and our cones love it best, etc...its just not going to contrast in a green environment with filtered light flickering down from above while shining it up....etc.
