@brentriddell to apply it first put the file tweakvec.py into directory home/pi/tweakvec/ on your sd card ( or other storage whre retopie is installed if that).
Then you can enter in terminal window on your PC or in retropie console next:
sudo python3 /home/pi/tweakvec/tweakvec.py --preset PAL60
you get true colors and pal 60 mode (must be sdtv mode = 1 in config.txt to get 60 Hz in all emulators)
But after next reboot you got standard ntsc mode ( with wrong colores), so if you want tweakwec fix always turned on you need write this command in file /opt/retropie/configs/all/autostart.sh It will be run tweakwec automatilly at every retropie start.
But in the end i've get right colors but also get "flickering" in some games. So to get flickering off i've used progressive mode ( write sdtv mode = 16 in config.txt)
Maybe it was helpfully too ( find my messages in the bottom of thread) https://github.com/raspberrypi/firmware/issues/811