Category Sidebox Color Change for Each Subcategory

I want to change the color of the categories sidebox background for each subcategory chosen from the horizontal drop down menu.

For instance, if choosing Sororities>>Alpha Kappa Alpha, I want the categories sidebox background to be green, but if choosing Delta Sigma Theta, I want the categories sidebox background to be red.

I know this will involve creating a separate style for each, but I wasn't exactly sure which files would need to be updated to make this happen.

I have added the Categories Dressing add-on as well.

I've also attached a image of how I want each subcategory landing page to look.

Link to my site is http://www.tregreekboutique.com/zencart

In the Classic template's css folder, there's a file CSS_read_me.txt that gives a brief explanation of how to do page-specific stylesheets, which is how I think you'd want to handle this.

If that doesn't explain it, search the forums for category specific stylesheet. There are several threads that explain it in more detail.