In the Adagio Ledger company profile, there is a setting on the first screen called 'Company Color'. Click the checkbox and also the button to the right in order to select the background colour. Your colour settings through Windows (32-bit, 16-bit, etc) will determine how many choices you have.
Typically I like to use the 'custom colours' if possible because you can make them as bold or as pale as you like. The standard 256 colours tend to be quite bold...