Absent from FM instructions manual, there is Red 4, with a yellow cockpit, much farer in the line in the same photo of ILM workbench.
Like Red 3, Red 4 has many large grey panels, completed by a few more shades of yellow panels this time. I seem to recall that one of the yellow signs near the canopy is not positioned on the right side, due to reference photos later identified as having been printed reversed.
Before weathering
After weathering
Note that you can also find discordant references about Red 3, 4 and 6, because there was a different game of the X-Wing, built for the pyrotechnics effects. These ones differed by a much lighter weathering finish and for most, showed large dark red flat areas on the wings, guns wing tip and belly.