What’s honor for?
With the new honor system came the little banners on the side of the summonners.
So how do I get one? I would look so pretty with a ribbon like that.
Also, what colors mean what type of honor?
Honor ribbons are awarded for 25 "honors". Or at least this is the case for Honorable Opponent. I have yet to see someone with such a ribbon on a friendly team, so I believe the requirement is higher.
As far as I know, red is for opponents (and therefore Honorable Opponents). I have yet to see a green (or any other color) so I cannot clarify this for you.
To get these ribbons, there's nothing much you can do other than play well enough, be friendly, etc. to be awarded Helpful, Friendly, Teamwork, or Honorable Opponent honors after a match.
P.S. To award these honors to other people, click the green "thumbs-up" button next to their summoner name in the post-match summary/chat room and select the appropriate honor.
Its not a set milestone number to get the ribbons, honors from people you normally play with aren't worth as much. Also it depends on your "honor/game" ratio, like getting 10 honors for 10 games is better than 10 honors for 1000 games