Every ones eyes are different, some people see reds better than greens and vice versa. Try both and see which one you seem to pick up better. To me I seem to pick up the red better since around me is so much green all around me. The red seems to just stick out. You should have enough extra filament to try both out a couple times.
I used a neon green and neon orange paint to increase visability only cost me 4 dollars,,neon green on the back and neon orange on the front,,works awesome,,Im an instinctive shooter so i didnt need the real deal this worked great,
I finally changed mine yesterday. It was kind of hard to get the red one out. I ended up cutting the melted ball at the front end and driving it back out with a small punch. The new one slid right in. The green is much brighter to my eyes.
I noticed the front Firesight on my 10/22 Takedown is the same diameter.(.060) I'm going to change that one to green also. It should show up good through the peep.