gsettings set org.gnome.desktop.background picture-options none
     gsettings set org.gnome.desktop.background color-shading-type 'solid'
     gsettings set org.gnome.desktop.background primary-color '#000'

For those of us in GNOME land. gnome-tweaks will let you strip the image file, but there's no UI for setting the background color, which defaults to a muted blue.