AAAARRRRHHHH! Reading the link I saw the solution I missed decades ago when I tried to use POV to make my PET create a colour display. Just reading the section

AAAARRRRHHHH! Reading the link I saw the solution I missed decades ago when I tried to use POV to make my PET create a colour display. Just reading the section on how they did 4 levels of grey scale was an eye opener. Yes, I got some colour by flashing squares on and off but it was unwatchable. I did the flashing for the entire screen together! Just by breaking up which squares flashed at different times I can now see would have made a big difference. Almost 40 years to learn what I did wrong.