Briefly...
In the upper right hand corner of each post, next to the post number, is a button. If you hold your cursor over that button, it mention adding to that posters reputation.
When you push that button, it gives you the option to Approve of Disapprove of that particular post. And a box to write why. When you do that, it will send that into the system, which affects the green (or red) boxes under that persons post count. Thus, the term "greenies".
In theory, the more "Approves" a person gets, the more green boxes they get, and a higher "rep" count. The higher the rep count, the more weight that poster has when giving rep to others, both positive and negative. It takes many "Disapproves" to change a poster from green to red, and similarly, just a few greens to change someone who is red at that time.
It's supposed to be an indicator.
The system is broken, in many way, especially in how it's used. And there is a cap to how much rep someone can have with many tied at "max rep". (Somehow, even I have hit max rep.) So it's not a terribly accurate system. But it still can be a fun way to compliment someone on a good comment, or a funny one.
***EDIT*** Too late.![]()
Okay, I got all that, but what the heck is a GRAY rep? I got one of those from someone and the comment was not very explanatory. (Actually there was no comment...)