>      LONG IF efHandle&
>        DIM whitePaint.rgbColor
>        whitePaint.red% = 256
>        whitePaint.green% = 256
>        whitePaint.blue% = 256
>        POKE efHandle&..teGrafPort.rgbBkColor&,whitePaint
>      END IF

Well, constants tool says _rgnColor is 6 bytes, and this means you might be
write followings...

DIM whitePaint.rgbColor
DEF BLOCKFILL (@whitePaint,_rgnColor,&FF)
efHandle&..teGrafPort.rgbBkColor&;_rgbColor = @whitePaint

This is only my guess, and the code doesn't be tested.