Int 10 Fn 1000  - Video - Set Single Palette Register (pcjr,ega,mcga,vga)  [V]

   AX = 1000h
   BL = palette register number (00h-0Fh)
      = attribute register number (undocumented)
        10h attribute mode control register (should let BIOS control this)
        11h overscan color register (see also AX=1001h)
        12h color plane enable register (bits 3-0 enable corresponding
       text attribute bit)
        13h horizontal PEL panning register
        14h color select register
   BH = color or attribute register value

Notes: on MCGA, only BX = 0712h is supported
   under UltraVision, the palette locking status (see AX=CD01h)
     determines the outcome

See Also: AX=1002h,AX=1007h,AX=CD01h