Google utilities generally have a nice, clear interface design which in some cases – such as Gmail – you can spice up with themes. But if you want to go one step further, you should install Google Redesigned.
This Firefox extension, as its name states, redesigns Google apps completely. The change doesn't affect all of the Google services, but just the most popular ones: Gmail, Reader and Calendar. The new Google look & feel is all coded in CSS, which means it doesn't affect any of the internal functionality. Also, getting rid of it is as easy as uninstalling the extension.
Google Redesigned is a dark, sleek style that gives your browser a very elegant interface – especially in the case of Gmail, which looks gorgeous. Dark tones are used in combination with shiny color codes that help you organize mails, feeds and dates respectively.
On the downside, if you don't like dark themes in general, you won't like Google Redesigned either: this is the only style available so far.
Google Redesigned modifies the look & feel of Gmail, Google Calendar and Google Reader with an elegant CSS-based dark style.
