The function color is (probably a pretty poor) way of describing a color I often see in UIs that prompts for a "secondary" action - examples would be a Close or

The function color is (probably a pretty poor) way of describing a color I often see in UIs that prompts for a "secondary" action - examples would be a Close or Cancel button, or administrative functions like "Edit your account", etc. The action color, on the other hand, is something that the app or site's creator wants to the user to do - "Sign up now!", etc.