Palette reg.s          index 00h-0Fh  ATTRIB

        There are 16 palette registers (0-15). Each register's layout
        is (bits 5-0):

                b5  SR  Secondary red
                b4  SG  Secondary green
                b3  SB  Secondary blue
                b2  R   Red
                b1  G   Green
                b0  B   Blue

        The color palette is a random access memory (RAM) that is used
        to indirectly map the data contained in the individual pixel
        locations of the display memory into colors. The palette
        consists of a RAM memory that is 16 locations long.