What is the deal with green followers?

Are mags with these better than others?

Obviously, I am new at this.

USGI thirties originally came with black followers.  They were thought to be the cause of failures due to the follower "tilting" in the body, so the green follower was invented.  It has longer "legs" to reduce the possibility of tilt.  I used to have a bunch of preban mags with black followers.  They worked fine.  I rebuilt them with new springs and green followers just for the heck of it.  Eventually I sold those to ban states and bought new USGI. Green followers came out sometime in the early nineties, I can't remember exactly when.  All current USGI type mags (Okay, NHMTG, Center, DH) come with green followers.   I say, if you have old mags with black followers that work, don't bother messing with them.  

Magpul followers have even longer legs and are shaped differently to prevent tilt.  But the green ones work well for me.  

Bottom line:  If you can pick up prebans with black followers for a reasonable price, do so.  Either (1) they'll work just fine, or (2) you can upgrade them with green or magpuls, or (3) sell them to someone in NY and buy new mags.

I have also seen green followers on older USGI mags that were not "improved" ie no "legs".

You are better off with anti tilt followers but any new mag with a green follower is more than likely good to go.