Controlling Sub-Pixels

ok so you have two options here: 1: Use only graphics:

DEF GSPSET X#,Y#,S#
 GPSET X#,Y#/3,GSPOIT(X#,Y#/3)AND NOT(&HFF<<Y# MOD 3*8)OR S#<<Y# MOD 3*8
END

2: Use sprites:

FOR I=0 TO 2
SPSET I,0,170*I,512,170,#SPADD+1
NEXT

DEF GSPSET X#,Y#,S#
 GPSET X#,Y#/3+170*(Y# MOD 3),#BLACK OR S#<<Y# MOD 3*8
END

(might be faster, but limits you to only part of the screen)