3
In your layout.css file (around line 32) you'll see something like:
background: #f2f2f2 url(../images/L1R1_container_bg.png) center top repeat-y;
The colors you're wanting to eliminate are actually embedded in the background image (L1R1_container_bg.png). You'll need to edit the .png file or you could eliminate it and set the background to a solid color if desired.
Welcome to XOOPS, and good luck!