From http://www.snopes2.com/music/info/greening.htm

"Even if there were strong edge reflections, there is no guarantee that coating a CD's edges with a randomly selected paint or ink would reduce or eliminate the reflections. The initial color proposed for the treatment was green, on the mistaken assumption that since the wavelength of the laser light used in CD players is in the infrared region of the spectrum, a green pigment would absorb it. Maybe so, but substantial infrared absorption is not an inevitable consequence of something appearing green. That's why I used black paint in my tests, on the assumption that an opaque black pigment is far more likely to be infrared-absorbing than semi-transparent marker ink. It certainly disrupts the laser beam more when painted on the surface of the disc."