Red button: https://img.skitch.com/20110701-bpf7rn6giqq64ya9ihr88pmfr1.png https://img.skitch.com/20110701-bpf7rn6giqq64ya9ihr88pmfr1.p... Green button: https:

Red button: https://img.skitch.com/20110701-bpf7rn6giqq64ya9ihr88pmfr1.png https://img.skitch.com/20110701-bpf7rn6giqq64ya9ihr88pmfr1.p... Green button: https://img.skitch.com/20110701-pff56qthuqr89t77d2x3u2smhj.png https://img.skitch.com/20110701-pff56qthuqr89t77d2x3u2smhj.p... Grey button: https://img.skitch.com/20110701-wwxrad2urrj1xjmanusme8w9w.png https://img.skitch.com/20110701-wwxrad2urrj1xjmanusme8w9w.pn... I now think the red works best too (but felt the same way as you about it at first). Other colours stand out against the red "Mail" and "Inbox" links, which gives a somewhat technicoloured dreamcoat feel to the UI. They could change the red links to green, but then they lose the connection with the red 'M' envelope character, as you rightly point out. A light grey might work, but probably wouldn't stand out enough for new users.