Default Color Palette

Is there a way to change the colors that show up when I press the Background color button. Custom colors stick while I’m in a session, but if I log out and back in, they’re gone.
I’m tickled pink (heh, color pun) that the plugin offers this button to begin with, so I can deal with it if I’m stuck with those 39 colors – I’ll just change my theme to work with them.