When -moz-border-*-colors is used, the rounding of the background color doesn't work. However when an background image is set it does work. The attached testcase (copied from 24998 and modified to use -moz-border-*-colors) clearly shows the problem. This is a real problem for my themes where I use -moz-border-colors to apply multiple colors to the color, and use rounding for panels, buttons, etc. But then the background color 'leaks' out of the rounded border...