User blog comment:Rakanishu2199/Best win rate - Blue or Purple team ?/@comment-186.206.168.96-20130115143708/@comment-5969046-20130115164943

True, but that happens very rarely and can not explain by itself the difference between the blue and the purple team.

In my opinion, the main reason is the same which can explain that sport teams win more games at home than when they're away - even if there is no direct difference between these games for each team. One feels more confident (blue team) while the other feels as the underdog (purple team) and this has a direct impact on the game.