One of the more annoying habits of the original C65 DOS is how the border color increases with each DOS error.
This 'feature' was introduced because early FDC revisions were not able to blink the drive LED to signal an error. On later FDC revisions (and of course, on the MEGA65) this problem was resolved, and there are - imho - no more reasons to flash the border.
So here's a little patch for the V0.9B.911001 ROM which disables the border color feature. Apply it with