FOR I=1 TO 4
 COLIDX=0
 YTOP=(I-1)*60
 FOR X=0 TO 399 STEP I
  IF COLIDX MOD 8==0 THEN
   RESTORE @COLOURS
  ENDIF
  READ R,G,B
  GFILL X,YTOP,X+I,YTOP+59,RGB(R,G,B)
  INC COLIDX
 NEXT
NEXT

@COLOURS
DATA 0,0,0
DATA 255,0,0
DATA 0,255,0
DATA 0,0,255
DATA 255,0,255
DATA 0,255,255
DATA 255,255,0
DATA 255,255,255