SET WINDOW -1020,1020,-5,5
SET COLOR mode "NATIVE"
FOR y=-2040 TO 2040
   LET x=MOD(y,255)
   IF INT(INT(y/255)/2)=INT(y/255)/2 THEN
      SET AREA COLOR colorindex(ABS(x/255),ABS(x/255),ABS(x/255))
   ELSE
      SET AREA COLOR colorindex(ABS((255-x)/255),ABS((255-x)/255),ABS((255-x)/255))
   END IF
   PLOT AREA: y,-5;y+1,-5;y+1,5;y,5
NEXT y
END