Google has started the roll-out of the new logo and Web UI design of the AdWords. The new logo is integrated into the navigation bar and reflects Google's move to the flat design, which was recently adopted in the flagship logo also.
Here's a screenshot of the new AdWords logo, tweeted by Rick Galan.
The old/current version of AdWords logo looked like this:
If you are still seeing the old logo in your AdWords account, no need to worry as Google has yet not made the official announcement of the new design.Google Starts the Roll-out of New AdWords Interface Design and Logo!,