Gmail's New Default Theme is a Step Backwards for Usability
This week, Google has been rolling out a new theming feature into Gmail. This is likely a welcome and overdue addition for many people who didn't like the default look of Gmail. Unfortuately for everyone else, along with the new feature, users are automatically updated to a new 'Default' theme for Gmail. This has happened in the past, but for the first time, this default appearance change is a step back for usability.
Fortunately, the new theme selector allows us to select the 'Classic' theme which returns Gmail to its previous appearance. With this ability to switch between the new 'Default' and the previous 'Classic' we can look at some specific ways that 'Default' is less usable than 'Classic.'
Contrast is Reduced on the Important, Increased on the Unimportant
Menu Text and Content Borders
In the 'Classic' theme, text is darker and stands out more against the white background. Additionally the border that runs around the body of the page is lighter. It does its job, separating the dynamic content of the view from the static menus and gets out of the way. Since this border isn't directly useful, it should be subtle, deferring attention the content.

Email Listing Text
Here the text has been changed from black to gray and the background has changed to a gray as well. If we use a contrast calculator, we can objectively compare this change. From the 'Classic' to 'Default' themes, the foreground to background brightness difference and the foreground to background color difference is reduced by 28%!

By default, Google is pushing people to a new theme with much worse usability. The contrast of interface elements has increased while the contrast of text has been reduced by over 1/4. It is good that gmail allows users to return to the classic theme, but it should not be necessary. The new 'Default' theme should be opt-in instead of opt-out because of its reduced usability.
Update: (11/25/08)
Kevin Albrecht has created a Greasemonkey script to force the listing text to black. To see screenshots of the change and download the script, head over to his blog.
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