When I colour coded my mirrors I had to pop the glass off. I only did this once the mirror body was off though. There was a couple of clips on the back of the glass. Whether you can do it without removing the mirror housing I don't know. The housing comes off easy enough though, 2 torx scres underneath which then gives you access from the bottom to undo a clip on the back of the glass holder and then the housing slides stright up and over.