This is my tiny contribution for this hackathon :-)
By coincidence, tomorrow we will have a local contests in my University in Madrid and we will use DOMjudge. We have three different problems categories with different level of difficulty, because our contestants have different programming background. We want those categories to be visible in the scoreboard.
I've changed libwww/scoreboard.php so each column belongs to a CSS class specific for the problem Id. After that, style.css can be changed with something like: