The Taranko colony was a Federation colony.
In 2370, the colony was in need of medical supplies. The USS Enterprise-D took up the needed supplies from the USS Lexington and delivered them to the Taranko colony. (TNG: "Thine Own Self")
According to the Star Trek: Star Charts, on the chart United Federation of Planets I, by 2378, Taranko colony had become a Federation member.