Color is subjective, everyones opinion is going to differ. As long as an engine that's suppose to be Buick red isn't sprayed Chevy orange. Light blue looks "corporate"...… '77 to '83/'84
401s were silver in the 63 Riv as well as the few 425s put in the Riv that year . Ted or one of the cat lovers would have to tell us about the 401s in 63 cats.
You did see that the engine color is silver in your file above for the 401 and 425 in the 4700 (Rivera) series?
That is the correct color but everyone uses the older green including me, because nobody makes the blue color.
My '66 425 has been rebuilt twice. Both rebuilders painted it the correct red. I would have preferred the green, but at the time(s) I didn't think to say anything about the engine color, so this is not to imply any criticism of the folks who painted it red.
My 1966 GS has a blue color engine. At the car show a guy wanted to argue with me that it wasn't a 401 because it wasn't green. So can anybody tell me why mine is blue not red?
It should be red, although there have been rumors of a few early 66 GS's having a green 401. There aren't any internal differences between the 66 green 401 and the 66 GS red 401. Check the engine code stamping to verify if it's a GS 401 (MR stamping) or the standard MT 401 found in the other models. The Buick green often looks bluish, especially in pics found online. The previous owner may have used that for reference in choosing blue.....or he just liked blue.