From what I know, Ribbons come from getting a certain amount of honor in a short period of time. I currently have the green one for Teamwork, but in the past I also had the blue and yellow ones for Helpful and Friendly. The only one I've not gotten is the Honorable Opponent one, but the reason may make sense shortly... My current numbers are 264/102/1993/514, though I earned all of my ribbons over a year ago.
When I started playing this game, I played very little PVP and stuck mostly to AI games. I found them to be way less stressful than PVP, and I still do. Sure, they're not nearly as challenging, but the entire atmosphere is different in AI matches. You'll still find the occasional troll or AFKer, but it really doesn't matter there. As long as the rest of the team can carry, it's fine. The AI isn't the best, and if you get fed you can make up for the disadvantage in numbers. But when you get matches where everyone is playing seriously (and I use that term very loosely), you find that this game becomes a lot of fun. Imagine that, right? A game being fun. Weird concept.
The relaxed nature of AI also attracts fewer ragers than PVP. They tend to play to defeat other people, and when they can't win, they rage at their team. While it is easier to win AI games, beating on AI isn't the same as winning against another human, so the more competitive players avoid it for the most part. Instead of "TOP OR FEED" you typically get "Mind if I go top? I want to test if Rek'Sai can go full tank." if anything at all is said in pre-game. In AI things, people usually don't care what champion you pick or where you go with it. To most, it's a 'First Win,' to others it's practice, and to some it's simply more fun than PVP.
Most of the AI games I've played have had people messing around not only with the game itself, but also each other. In AI games, I've seen people 'race' their lane partner to the outer turret, some even blowing Summoner Spells to win; amusing emote spam like Vel'Koz's /Dance spam while behind a teammate (it looks like a TOTALLY different kind of 'dance') and Viktor's /Laugh spam causing him to juggle his staff between his normal arm and his third one; and a lot of hilarious chat logs. This is an example of one I saw recently...
A Yi was practicing the new jungle, and asked if one of us could try to 'steal' Dragon while he solo'd it, so he could get better at timing Smite properly. He missed by a fraction of a second, and I got it with Viktor's Death Ray over the pit wall (I did actually ward it, to make it more 'fair'). Then THIS happened.
: preseason is a sadistic jerk
: ^
: I'll get my drag on again xP
: We're all learning something this game, it seems...
: that was meant to be a swag pun
: What.
: did not realize the connotations until enter was pressed
: This will hopefully teach you why using 'swag' at all is bad. XD
The entire team had been offering suggestions about the new jungle all game, and after that other forms of (sometimes unwanted) advice started being thrown around. I honored the entire team after we finished, and received a few honors myself.
I do mostly PVP now, but if I'm ever in a rut or tilting, I'll do a few AI games to practice specific concepts of the game or just cool down after particularly annoying PVP matches. I've noticed that people still honor in PVP as long as you've got a decent attitude, but honoring is way more common in AI games.