VIEW (Visual Input Enhancement of the Web):
Instant colourization of grammar structures, instant learning activities from any page on the web. Supported languages: English, German, Spanish.

VIEW Toolbar – Firefox Add-on (Screenshot taken on Linux Mint 64-bit, extension is available on all major operating systems (Windows/Mac OSX/Linux)

Colourized prepositions in a Guardian Article published two hours ago … (2 clicks and 10 seconds away)!