According to Retroblackrifle.com, the furniture on the 601 was painted green. It's possible that different lots of paint resulted in slightly different shades, but what I'm seeing on their website looks very similar to what's on Brownell's website.
Link to Retroblackrifle.com's entry on the Colt 601.
I believe I read somewhere that the green-painted furniture on the 601 was later repainted black - except when it was outright replaced with newer production black furniture.

