from the danroy info:
basicly, orange was the color of the car V8 - gray for light trucks, green for heavy trucks [usually w/ governors] - in 57 the 283 was gray, yellow, green, black, orange depending on options - couple years in mid 60's 283 and 327 both orange in car or truck, then back to 283 gray, 327 green and the gray became bluish gray with nearly all truck engines the blue/gray
yer 66 should be the blue/gray, kruiz
Bill