A colonist was an individual who lived in a colony.
Jovain Pallis was a colonist on Mars. He murdered two of his crew mates, Marissa and Uther. The Second Doctor took him to an uninhabited planet in the TARDIS and left him there. (PROSE: Dust)
Several humans, led by John Robert Ashe, were colonists on Uxarieus after leaving Earth in 2471. (TV: Colony in Space)
Laroq was a Phoenix colonist who met the Fifth Doctor, Erimem and Peri. (AUDIO: Three's a Crowd)
Ted Henry was a human colonist on Teuba. At the time of the Sixth Doctor and Evelyn Smythe's visit, he was the president of the colony. (PROSE: The Diplomat's Story)
Dimitri Molokomme was a colonist on Yemaya 4. He was in charge of agriculture for the colony. (PROSE: Sleepy)
Sharma was a human colonist on Ramosa. She used to run the recycling plants. (AUDIO: The Reviled)