I'm not liking the big red "Compose Mail" button and labels. Red is usually used as an indicator of warning and error messages, and the giant red button really jumps out at you when you first see the redesign.
If you're trying to move away from the "40 shades of blue" while keeping a fun and playful feel, why not use green?
Done. Also, on closer inspection, I think I see the rationale for their decision. They may have chosen red because it looks like red may be the "official" color of Gmail -- notice the red line on the top nav bar above "Gmail," along with the red "M" in the logo.
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.
