Given that it is the difference, matching areas are black. The areas that are no black are faint. You might want to play with your monitor's contrast settings.

Given that it is the difference, matching areas are black. The areas that are no black are faint. You might want to play with your monitor's contrast settings. The non-black areas are clearly visible on my ancient laptop's not so great monitor. Regardless, here is the difference after auto-levels adjustment in Gimp https://imgur.com/a/XDHQlpu https://imgur.com/a/XDHQlpu