Returns the highest color that can be passed to the SetColor procedure.
function GetMaxColor: Word;
As an example, on a 256K EGA, GetMaxColor always returns 15, which means that any call to SetColor with a value from 0..15 is valid. On a CGA in high-resolution mode or on a Hercules monochrome adapter, GetMaxColor returns a value of 1 because these adapters only support draw colors of 0 or 1.
Must be in graphics mode.