I went to Themes. There I can click a button which says “pick color.” Unfortunately all it does is take me to a small pop-up which shows the colors and then fades to a blank pop-up called “about blank.” When I clicked “Check if you want to change manually,” I changed the color myself, based on a color I found on the web. It changed it back.
I do not know why this does not work. Does anyone have any ideas?