What's the deal with coloring CD's and/or tray mechanism

First worm out of the can.

It used to be conventional wisdom that treating the edge of the CD with a green marker would lessen the scattering of the laser's reflection while reading the disc, or something like that. That also led to whole disc covers and some going so far as to treat the insides of the disc assembly with various applications and so on. 

It was a terrible time for audiophiles and left enough of a latent impression which led to the hastening of computer audio, with all it's dos don'ts, and conventional wisdom.

All the best,
Nonoise

The intriguing thing about the whole Green Pen and painting the outer edge of the CD or the CD tray with green ink, the complementary color of red, thing is that the CD laser is essentially invisible light in the near infrared part of the spectrum. Thus theoretically at least green or any other color should have no affect on the sound since infrared light, being invisible, has no complementary color that could absorb it (before it makes its way into the photodetector).

😄

far better tweak is to draw green rings on your power cables

Hey, mods! Randy’s stalking me again!

If edge supposed to reflect infrared then it should be gold marker, but if it supposed to kill reflections it should be black.  Green doesn't make sense.