I like to distance myself from red for actions, unless it is performing a specific delete/cancel/undo type action - where the user will either do something that they may regret later, or to take them out of a flow that they are already in. That's just a personal preference though - I know a lot of big brands use it to reinforce the urgency needed to take an action - "Get it before it's too late!" would be less urgent if it was on green, rather than red.
Also I think it depends a little on the site wide colours, and also the specific action you are taking. A blue search button looks way more natural to me than a green (or red) would (Google and eBay wouldn't look right with another colour). A "Register" button on the other hand less so.