Does that actually add markup to colorize the code or does it just wrap it in <pre> tags?
Long answer: Check this link:
http://code.google.com/p/vimcolorschemetest/
At the bottom, click on one of the provided languages. This will give you a preview of what the command actually outputs. The page itself states, "To generated these pages, I used the TOhtml command in the Vim 7.2 distribution to generate the html files inside the iframes". Just note, the font won't be as disgusting when you actually do the conversion.