Category Page's Help with background

i have a Website , but the person who made it i can no longer get a hold of at the moment and i am making a few changes, everything i have done so far i am ok with but now i would like to remove the square color from my category pages
for example my main home page is http://www.inticeonline.com working fine and i like the color behind the main content a darker grey then the white

but when you go to http://www.inticeonline.com/category/photos/
i dont want it to appear there, because i removed the side bar but now that square is still there, how can i remove this? please and thank you