Colrain is a town in Franklin County, Massachusetts, United States. The population was 1,606 at the 2020 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area. Colrain was first settled in 1735 as "Boston Township No. 2", organized into an independently governing town body in 1745, and was officially incorporated on Jun…Colrain is a town in Franklin County, Massachusetts, United States. The population was 1,606 at the 2020 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area. Colrain was first settled in 1735 as "Boston Township No. 2", organized into an independently governing town body in 1745, and was officially incorporated on June 30, 1761.