Hi Lisa, There are other ways to try to change the background color but no simple way. Another way you can try is using the Doodle Tool (towards the end of Effects) to paint on the new color. You can hold down the Shift key to constrain mouse movement to straight lines. This isn’t a simple approach though and will take a long time with a large collage.
Another technique is to go to Advanced > Pro Editor > Pixlr Editor and use the Paint Bucket icon to fill the new color (you can pick the color by double clicking the color picker towards the bottom left of the toolbar). This doesn’t always work perfectly though (for this purpose). After you’re done click File > Save to save back to Ribbet.