Well, just to make it confusing, there was also an early smaller set of 600 passenger cars, something like 1915- 1923 or 27, something like that. They are smaller and of an earlier design. I don't have a picture handy, but you can probably look them up for reference. Either way, you would want the later ones like I posted above to match your loco. Red on Red was also one of the more common colors of the later 600/2600 series passenger cars so maybe great for a Christmas train.
The 1690 cars are a bit smaller, probably a bit to small to look right in my opinion. Lionel also some those same cars. I think they were born out of the Lionel-Ives transition period and thus were labeled Ives and later Lionel for their life. They would look good with something like a 259E or 1688/1668 027 Torpedo locos.