I just got the e-mail. The default Google color palette, Seaside (formerly known as Mother Earth) will be changed to Open Air, a new palette containing the same set of colors, but without the blue border.
We’ve found that many publishers prefer the cleaner look of this palette and have also seen that a blended color palette performs better for them — attracting user interest while still maintaining the distinction between ads and content with the ‘Ads by Google’ label.
Please note that this change will only affect your ad units where your ad code does not specify colors.* For all other units, your color selections will be retained.
*You can check if your ad code specifies colors by looking for any “color” tags such as “google_color_border” or “google_color_bg” in your HTML. If you find any color tags in the code for an adunit, this unit will not be affected by the change.
In order of appearance : Old default color (Seaside) and the new default color palette, Open Air: