Color Table Size       AL = 000h
  Input:
     None:

  Return:
     BX    The size of the color lookup table.
     CX    The maximum color number allowed.

The COLOR TABLE SIZE query is used to determine the maximum number of
colors supported by the hardware. The value returned in the BX register is
the number of color entries in the color lookup table. The value returned
in the CX register is the highest number for a color value. This value is
usually the value in BX minus one; however, there can be exceptions.