Excellent. Thanks very much. I've made them black and will now set about fixing some of the other poor colour decisions, e.g. the body of the top post of a thread being an unreadable gray which puts me off reading it through no fault of the author.
@-moz-document url-prefix(http://news.ycombinator.com/){ .comhead a font { color: #828282 !important; } }
(how to create a user stylesheet: http://www.squarefree.com/userstyles/user-style-sheets.html )