Paypal Payments Page Background color

Hi I'm new to ZenCart and am in the process of configuring our first installation. It is standard 1.3.8 with a highly modified version of the "mostly grey" template. We are currently trying to get the paypal linkage the way we want it.

Reading over the Paypal HTML How-Tos there is a section describing
HTML Variables for Displaying PayPal Payment Pages and in that section they discuss an optional variable cs that allows you to set the background color of the Payments page to black.

I've read the FAQs, searched the forums, read two different ZenCart books, AND searched through as many of the files associated with Paypal in the zencart hierarchy as I could find. I can't find where I can set this option.

Can someone point me in the right direction?

Thanks in advance.
GK