Use an image for the Page Background. Then use Focus to add content. Focus has its own background, which you can set to any solid colour that you like.

There are many Focus sections that provide a variety of content layouts. You can add or delete modules inside the Focus to make it exactly the design you want! 

I think i understand what you are asking.  Your text is not legible on top of the image that has been placed as your background.  You might notice that there is a knob above the image picker that allows you to adjust the brightness.  Above a certain threshold Bookmark will make your text lighter or darker to compensate.

Hope this helps