Help, editing template

[Shinitenshi]

Under "Define Pages Editor" I wanted to add some information to give my website a little more content. I added some images but the background is transparent, so the images look out of place. What can i do to change the background of the "define_main_page.php" so the images blend in a little more by adding a white background.

Here is a picture so you can see my issue:
[SCR]http://goldcoasttechs.com/misc/images/help.jpg[/SCR]

you see how the boxes to the left have a solid gray color? i would like to do this to the center but with a white solid color.
thank you!