This will allow you to only effect the background of your description:
<table bgcolor="putyourcolorhere" cellpadding="10"><tr><td> (your
regular description goes here) and put </td></tr></table> at the very
end of your description.

Font colors are done by adding a color element to your font tag like
this:

<font face="arial" color="blue">put your text here</font>

<p align="center"><font face="Garamond" size="5" color="#0000FF">
<span style="background-color: #FFFF00">
<marquee behavior="alternate" scrolldelay="60" width="780">
Thank you for taking the time to look at my auction item!
</marquee></span></font></p>

<span style="font-weight: 700; text-decoration: underline; 
background-color: #FFFF00"> Underline.