Port 3C0,14  -  Color Select

          1111 xxxx  Reserved
          xxxx 11xx  S_color 7/6
                       In modes other than mode 13h, these are the two
                       most-significant bits of the 8-bit digital color
                       value to the video DAC. In mode 13h, the 8-bit
                       attribute is the digital value to the video DAC,
                       These bits are used to rapidly switch between sets
                       of colors in the video DAC.
          xxxx xx11  S_color 5/4
                       These bits can be used in place of the P4 and P5
                       bits from the internal Palette registers to form the
                       8-bit digital color value to the video DAC. Selecting
                       these bits is done in the Attribute Mode Control
                       Register (3C0, 10). These bits are used to rapidly
                       switch between sets of colors in the video DAC.