Well, nice post and welcome! I do believe you are correct in that the Swedish "Green" may have evolved over the years, however one way to see an original finish is to purchase some parts, or a parts kit and they most often retain the original color. Another way, and one that I chose to follow was to contact Stan's son, John Andrewski. He and his dad built the original Wilson tube guns (200) and he has a ton of experience in this arena. That being said, the M45B: 1954, Swedish Green paint over gray, full auto only, riveted magazine well, V2 receiver end cap (reinforced), smaller hole shroud, was green and John finishes most of his "re-do's" in a Green that is as close to the original as possible.
Nice looking gun and welcome again!