RGB Video Output (PC Engine Duo)
It is common to install an 8-DIN Mega Drive 1 / Genesis 1 AV port on the PC Engine / Duo / Duo-R and use the additional 3 pins for RGB output.
You can use the existing composite video for SYNC, or disconnect composite and wire from the HU6260 pin 44 (CSYNC) directly to the composite pin of the AV port to use a cleaner sync signal.
The R (pin ), G (pin ) and B (pin ) all come from the HU6260.
Notice the pinout of this mod uses different signals than the Master System 1 AV pinout, so you would want an RGB SCART cable wired correctly for this.