Styling Pings

Hey guys, I’ve been going crazy becuase I don’t know what to change to do what I want, since I’m not finding any tags to do it.
I don’t want to split comments and trackbacks, I like the idea of having them together, but how can I highlight differently the pings from the comments? For example, what should I change if I want the background of the pings to be light-grey and the background for normal comments white? I can’t find different tags in the comments template and I really don’t want to screw the file, so can anyone help me with this? Any hack or plug in you could recommend me?
Thank you very much, I hope you understood that, my english’s gone really bad lately…