'Colour bars. RGB(1,2,1) 4 bit with R G & B components
mode 2
dim integer R,G,B,x,y=1
dim integer xx=mm.hres-1,yi=mm.vres/16
for R=0 to 255 step 255
  for G=0 to 3*64 step 64
    for B=0 to 255 step 255
      box x,y,xx,yi,,rgb(R,G,B),rgb(R,G,B)
      box xx-60,y,xx,yi,,rgb(R,0,0),rgb(R,0,0)
      box xx-40,y,xx,yi,,rgb(0,G,0),rgb(0,G,0)
      box xx-20,y,xx,yi,,rgb(0,0,B),rgb(0,0,B)
      y=y+yi
    next
  next
next