Color select           index 14h  ATTRIB

Layout  b3-b2  C67  Color 7,6
        b1-b0  C45  Color 5,4

        This register contains two fields which, combined with the
        output bits from the palette registers, determine the 8-bit
        address used to select one of the 256 color registers. It is
        possible to segment the color registers into 16 groups with
        each group consisting of 16 registers. This is useful because
        in all but mode 13h, the maximum number of simultaneous colors
        that can be displayed is 16. Thus, it is possible to rapidly
        select from 16 different color palettes by simply modifying
        the C45 and C67 fields of this register.

        A second technique segments the color registers into 4 groups
        of 64 registers each. Thus, it is possible to select from 4
        different EGA palettes by modifying the C67 field of this
        register.

- Color 7 and color 6 (bits 3-2)
        Address bits 6 and 7 combine with the six output bits from the
        color palette to form the eight address bits to the color
        registers.

- Color 5 and color 4 (bits 1-0)
        Address bits 4 and 5 combine with the two address bits from
        the C67 field above and the four low-order output bits from
        the color palette to form the eight address bits to the color
        registers. This field is used only if the IPS field of the
        Mode control register is set to 1.