Dunno whether this will help, but here's a 2006 post from Hyperscale:
"According to the late Pete Bowers it was yellow,and since it looks glossy I'd say its Orange Yellow 13538.
I can only find one overhead picture of a four engine Naval aircraft from that time (an R5D) and it has the National insignia on the left wing and a 3 digit number followed by NATS on the top of the right wing,another R5D from the same time period shows only NAVY under the left wing.
If the airplane in question followed suit then it should be 309 NAMU on top of the right wing and NAVY under the left wing. The airplane's full BuAer # was 32309 (ex 44-40062) and she was used as a one of a kind test and drop ship for the Naval missle testing program at NAS Johnsville. Note the blisters in the waist windows. She's carrying KB3N-1 anti-shipping missles."
Les (The Voice of Authority --
THE - Home)