Google has now introduced Ad Styles for the 'new' AdSense interface.
Ad Styles is a new way of managing the color palettes for your AdSense ads. Google said this is a feature that was "missing from the old AdSense interface" and now you have it on the new interface.
When you edit a style, it will automatically update all the ads using that style, which can be a good and bad thing. So keep that in mind.
Here is a screen shot of the ad styles console: