Hallo!
I second that - I think it would be a very useful feature. However, I think the colour should be quite subtle so as to not look too much like an error (red) or another alert message. Perhaps it should also be an option, so that people can turn 'colour mode' off if they really do just want black and white (or perhaps slightly better performance).
yes, maybe this could be something like a debug-mode ...
LG Georg