Svg files can be stacked in a web page and can easily be manipulated using colour matrix filters. In this case the svg files are being manipulated to highlight the differences between two versions.
The aim is to show changes between two arbitrary revisions of board or schematic.
Yeah, on my big Frankenstein script I will workaround this. But it would be awesome to have something fixed on Kicad too.
I will be off by the rest of the week, I. not sure if I am going to have internet until Monday. Could someone file a bug report for me? Maybe like linking this discussion here since it has some pictures to help.