The information that I have (from an article written by Bob Hensel) is that the 65 truck 250 was Blue/Gray. The 230 Blue and 292 Green-Dark/Gray. The 1966 is listed as 230 Blue and 292 Green-Dark/Gray there is no 250 listed. Since my books show a Hi-Torque 250-6 cyl was used in Series 10 thru 50 for 1966 I must assume that it was over looked in Bob's list. I would also assume that the color was Blue/Gray.
My info. indicates that a 292 engine was an option in the 1/2 ton thru 1 ton trucks in 1966.The 250 being standard.The 292 has taller side covers than a 250 and is the green color.Side covers are about 6" tall VS 5 on the 230-250...Time for a casting number check.