This post isn't meant to start an argument about syntax highlighting in the context of code. It has its benefits and drawbacks, and I don't care whether you like it or not.
That being said, people arguing against it sometimes show a paragraph written in regular English with the different parts of speech highlighted, to show the absurdity of syntax highlighting. I don't believe that is a valid argument. Prose is read linearly, while code is read more chaotically. When coding, your eyes often jump across the place - and color can help you quickly find code matching the pattern you're looking for.
More generally, the distinction is between passive reading, and editing. Thus, here's my stupid idea - what if one actually used syntax highlighting for editing prose? Colors as vibrant as often used for programming would be too distracting, but toned down ones could perhaps help you scan your work easily. Different parts of sentences would be easier to find, repetetive sentences might stand out more, etc.
I haven't implemented this, and I'm definitely not qualified to judge how horrible this idea is. Still, I guess any thoughts are welcome.