Change the Background Color?

Click on the page you want to change the background color on, then go to the Background panel (in the right side Panels area) and turn on the Background Color checkbox. Next, click on the color swatch that appears to the right of that checkbox to bring up the color picker where you can choose your background color (by default, it shows white, black, and some popular shades of gray as little one-click swatches, but if you drag the HEX slider, over on the far right, up toward the top, the gradient in the middle changes from blacks, whites, and grays into a color gradient). Also, if you want to change the background of just one particular page (like I did here), turn off the Apply Background Globally checkbox at the top of the Background panel or it will change all the pages in your book to that color (unless, of course, that’s what you want to do).