When you are on a user contributions page, that user's name is stored in a cookie. Whenever you're on a history page, the script will highlight all edits by the username stored in the cookie.
By default, the highlight is light green, but you can set it to any colour you want, by setting the
window.hh_highlight
property wherever you have the script installed. For example:
window.hh_highlight="red";mw.loader.getScript(...);// History Highlight
