People who use green for mana bars instead of blue for mana bars... that's just hubris.
Of course what he means by this is that developers who defy basic gaming trends are setting themselves up for failure. To continue the mana bar metaphor, players have become accustomed to blue mana bars and green health bars from a long history of games. Mixing up this very basic element will only make a game less accessible. On the flip side of this, however, is innovation. If no one breaks the traditional molds, we may never see better games. But at the same time it's hard to argue with Bethke's example: why change a game element that players are accustomed to? It could make the difference between a game that's intuitive and quickly picked up by new players and a game that loses players before the tutorial's finished.
