Cannot change background color in Ubuntu 13.04

Solution 1:

It's a confirmed bug. See the bugreport in Launchpad: Unable to set solid colors and gradients as desktop background in gnome-control-center

Solution 2:

Initially you should be able to pick & use either the default solid blue, (#023c88) or that blue with a vertical or horizontal gradient (defaults to secondary of #5789ca

However once you open the custom color selector & choose anything then entries are made in rgb(X,XX,XXX) which produces black & you can't change that from Appearances > Background

I'd suggest opening dconf-editor > org.gnome.desktop.background & either reset color-shading type, primary color & secondary color back to defaults or enter the color(s) you wish directly using #XXXXXX