2
punivers:
Your image shows a right column with a background color we'll call X. This same color is defined as the background color for your right blocks.
In your theme.html file, you'll see that the right column is built using a TD tag labeled "rightcolumn".
Open your style.css file and look for the options related to this selector. You'll see there are four:
td#rightcolumn
td#rightcolumn th
td#rightcolumn div.blockTitle
td#rightcolumn div.blockContent
In the first one you'll have the background color for the whole column. In the last one, the one for the block. If you want these colors to be different, just change their values in the CSS file.
Don't forget to clear your cache and delete the files under templates_c to see the changes you've made.
Cheers.