SirG asked for something like this in the request thread, basically it makes things black and white.
sulasno put up a bookmarklet to do it so I thought Id turn it into an extension.
NoColour.crx (14.3KB)
The first icon selects between black text and white background or white text and black background.
The second button turns it on and off. If its on and you go to a page or refresh then it will be rendered the selected colours.

Great !
and thanks for sharing