That Clancy novel is "Red Storm Rising". Probably my favorite of his works. The M1s in there are from the 11th ACR at the Fulda Gap area of West Germany. The story is set in Summer 1987 if my time reference deductions are correct. At that time M1s were in the overall Forest Green, although the 11th was known for field applied camo schemes with mud or whitewash as needed. Also that was about the time that the IP M1 was coming into field service, so that would not be a stretch to model. The IP M1 shared many features of the M1A1 but still retained the 105mm main gun.