4
It's all theme dependant and can be edit through the CSS as mentioned. View source and look for the ID thats being used and change to suit your tastes.
A good example to see in action would be to open up the theme block to your webmaster account and choose different themes to see how each affect the forums.
Personally, I think the new feature should come with it's own CSS file, just a few basic functions that don't interfere with most CSS definitions would be enough. Then again, that would clash with some themes, so this might not be an option. You could edit the template and create your own ID's if you wanted, but I'm not sure how much work you want to put into it.
Anyway, good luck!