JW51,
I think that at least some high pressure 235s were a lightish gray because the 1954 engines (the first high-pressure truck engines) that I have seen have been painted gray (a relatively light gray with no apparent blue).
Also, I think that GM might have stated blue-gray or bluish-gray if that had been the color; but, in the 1954 Technical Specifications manual, Chevrolet/GM states "the new engine is painted gray". Who knows what shade of gray they were referring to (as we know know, there are at least 50 shades of grey/gray)? I know that I do not know the shade of gray.
Also, the engine-colors article written by the VCCA member (link is in a post above) refers to blue-gray until 1954. From 1954 and after, the 235 engine color was described as gray (or green - go figure). I think that author noticed a change in color in 1954?
It looks like a color change occurred in 1954 (perhaps related to the change from low-pressure to high-pressure oil system).
I also think that there was not an exact color/hue/darkness for earlier blue-gray or later gray - it depended on whatever shade of gray or blue-gray could be mixed when an engine had to be painted in the factory or on the assembly line.
Regarding the Filling Station color being the same as found on NOS parts: what years? Jim Carter and Bill Hirsch state their colors come from NOS parts and/or "unmolested" engines.
We/I will never know, but I am interested here is seeing opinions on the darker blue-gray.
