Function: highlight-changes-rotate-faces

Rotate the faces if in Highlight Changes mode and the changes are visible.

Current changes are displayed in the face described by the first element
of `highlight-changes-face-list', one level older changes are shown in
face described by the second element, and so on. Very old changes remain
shown in the last face in the list.

You can automatically rotate colors when the buffer is saved by adding
this function to `write-file-functions' as a buffer-local value. To do
this, eval the following in the buffer to be saved:

(add-hook 'write-file-functions 'highlight-changes-rotate-faces nil t) (fn)