In your noncgi folder, there will be a folder called Styles
in there will be files. open them, and find the line that starts
q!TableColorStrip!
edit that line to be something like
q!TableColorStrip! => q~#000000" style="background-image: url('/grad1.gif');~
This will get undone when you edit styles in the CP, so remember how to do this.
you can do something similar for the line starting q!CategoryStripColor!