Tim-
I\'m very much a newbie too!
The tabpane.css is located in includes/js/tabs/tabpane.css
When you open it up, you need go to .dynamic-tab-pane-control .tab-page and change the background color to whatever color you desire. I changed mine to black (#000)
.dynamic-tab-pane-control .tab-page { color: #333; font: 11px Tahoma, Helvetica, sans-serif; background: #000; padding: 5px; position: relative; z-index: 2; top: -2px; width: 97%; float: left; border: solid 1px rgb(145,155,156) }
THen go to components/com_rsgallery/rsgallery.css and change table.adminlist and table.adminform background color in the same way as above.
Hope that makes it clearer!
Sally