Rage - this new feature was added to the game in the recent update. Rage indicates how aggressive a particular player has been recently toward other players.
So what does this mean exactly? It means that when some player does destructive damage to another player, his rage meter goes up and this is visible to everyone else looking at the player's towns. This can serve as a warning to other players to beware - or actually an introduction to attack, because attacking an enraged player earns you Colorado Stripes! Those stripes are essential for the War Victory. The more enraged a target player is, the more stripes you can earn! This does not cancel the fact that you can also earn stripes from players of a higher age than you.
That being said, attacking a highly enraged player which is also at an age above you will allow you to earn the maximum amount of stripes!
The Onslaught which targets enraged or higher-age players has changed to Heroes Onslaught and has a different icon for simplified identification.