Other forms: colonials; colonially
The colonial period of United States history occurred before 1776, when America was still 13 colonies under British rule.
You can use the word colonial to describe an inhabitant of a colony ruled by another country, but you wouldn’t call a painter living in an artists' colony a colonial. On the other hand, ants, which live in ant colonies, are colonial insects. British colonial is a style of furniture the British favored for their houses and tents in India or on safari in Africa — when India and parts of Africa were British colonies.