You would be correct with spring and summer.  Spring is [i]haru[/i] (when [i]hanami[/i] occurs hence the pink), summer is [i]natsu[/i], autumn/fall is [i]aki[/i] and winter is [i]fuyu[/i].  The group could be known as the [i]Shinobi no Shiki[/i] (Ninja of the Four Seasons).