I've been programming for 30 years now, I remember back before syntax highlighting. I had a bug that I couldn't track down - it took forever. I had an infinite loop that would only run 3 times and then exit.

Here was the problem:

  for (int i=0;i<3;++i) {
    /* Initialize important things.
    frozzleTheNozzle();
  }

  while (1) {
    /* Do ALL THE THINGS. */
    makeSureTheNozzleStaysFrozzled();
  }

Syntax highlighting prevents the entire class of bugs from happening (as do compiler warnings, but hey). I told one of the other guys I was working with, and he introduced me to emacs which had just gained font-lock mode.