Maybe it's just late at night, but how does this work? I understand the words "invisible separator", but for lack of better phrasing, I don't see an invisible separator.

Between the r and the e there is a U+2063 "invisible separator"

Ahh, thanks, that's the actual name of the character! 3am and I've already learned something new for the day.

Between the R and E of red there's some extra character.

My font shows it as a missing character box.

I'm guessing that it just breaks the 'red' into a value which is interpreted as whatever the hex is. (See the chuck norris links posted in this thread).

Red text in source code

http://jsfiddle.net/A6TQK/