[Ron Smith]

Ed,
Can you post some good clear photos? There are ways to tell, but hard to discribe to someone not atuned to notice. It's a matter of experience,and knowing what to look for.
The original blue on old Colts would appear to have a satin hue. The color is a deep rich blue. The roll marks on the slide should be deep and crisp. All sharp edges should be sharp and straight. Hold the pistol so that you can sight down the flat sides of the slide. The light should reflect a glass smooth plane, with no waves or ripples.
Also on a pistol that old. The sharp edges should show some slight wear. The grip straps may show slight patina (turning brown), or show some thinning of the blue.

Ron