Gmail Introduced Themes!!!

Just few mins ago, I have logged into Gmail and discovered some changes on interface! I was looking for New Features link at right-top. But did not found. Then I saw a message on top that they introduced themes and colors. I browsed to the Theme tab from settings and tried themes one after another. But none of them suits me. I did not like a single theme. None of themes are comfortable for my eyes. Most simple themes has too many white spaces that were making reading unpleasant. I tried some other non-white themes. The background of those colors are not also comfortable for my eyes.

I am now wondering how to switch to previous looks. I hate current themes :(.