[Koha] Customizing the Koha OPAC on Koha 3.14.02

I have installed Koha 3.14.02. I would like to change the black background on the Cart and List menu to something else. In addition I would like to put a banner above the Cart and Lists region, but cannot figure out how. I will also want to change the white background for the OpacUserMainBlock to something. I will appreciate any pointers. Kind Regards, Admire Mutsikiwa ICT Projects Manager LibrariesUniversity of Zimbabwe