Ok, you will need to do the following!
in your
forum/themefiles
dir there is a file called additional-forum.css, open it and copy all its content to your theme css style.
In your case this should be located in
geeklog/public_html/layout/clean/ directory.
You will notice the most change by editing the following lines!
Text Formatted Code
.forumclass1 { text-align:left; background-color: #BFBFBF; }
.forumclass2 { text-align:left; background-color: #CCCCCC; }
.forumclass3 { text-align:left; background-color: #EFEFEF; }
.forumclass4 { text-align:left; background-color: #CCCCCC; }
Note you can customise the forum to suit your needs completely, if the way Blaine has worked the css into the templates doesn't suit you, just edit the forum templates once you are comfortable with the different classes for the forum styles!
Dazzy