Sometimes in my travels, I hit a button that makes enemies turn gold for a short while. What does that mean? I am assuming, like most everything in the game, it is coin related, but what specifically is going on?
Enemies turn golden when Mario/Luigi touches a Gold Ring. In this state, the enemies will give you coins when defeated instead of points and may spawn coins while they are alive (e.g. throwing coins at you).
You can find the specific behaviours for each enemy at MarioWiki