The method with the jpg is the worst thing. You're just adding extra load on your pages for absolutely no reason at all. Now if you said you didn't want it on all cells to start off with, I would've saved you and me the bother of giving you css which is no use to you.
Code:
<style type="text/css">
.waynescolor{
background-color:#ff0000;
}
</style>
Then for the cells you want colouring in,
<td
class="waynescolor">