Applying background color to ordered list numbers, NOT content

[HaLo2FrEeEk]

I need to know how / if it's possible to apply a background color to a ordered list item's numbers, and not the content itself. I've tried:

ol {
   background-color: #FFFF00;
   }

But that does the opposite, applies the background color to the list's contents, but not the numbers. I'm making a syntax highlighting script that shows line numbers and I need to be able to clearly separate the line numbers from the code.

Can someone help me achieve this please?

[HaLo2FrEeEk]

That's much more elegant than my solution, but it doesn't work in IE7. My logs show I'm still getting a decent number of visits from IE7 users. Here's the page with my solution:

http://infectionist.com/extras/csharp/haloscreenshots/misc/blf_struct.php

It even works on my Android phone.