If you want to change the left side of the Explorer background here you go.
Open it in Skinstudio then Edit Explorer/IE Shell Parts. Go to Edit Vista/7 Explorer Parts. The second item down "Folders Bar. Leave the graphic that is in there alone. Click on that and go to Extra Settings Now you will see Background Color (Win7). Click on the drop down box on the right. if the color you want isn't in there you have to click on the button next to the drop down box. This will open Edit Colors. Now you will have to click on Apply new color preset. Then go in and make it whatever color you want and click Apply. Now you can go back into the drop down box and see the color. Click it and hit apply the WB it will ask you to save say yes.
Please note. After you modify someones skin it for you own personal use and not to be given out.