The Mushroom Colony is a gated complex of several buildings, operated by a group of Mushroom space colonists, and is located on a desolate planet.
The Mushroom Colony was only ever seen in The Super Mario Bros. Super Show! episode "Star Koopa". Darth Koopa wanted the Mushroom Colonists to surrender their planet to him, as he was threatening to destroy it with his Birdo Ray if they failed to comply.
After escaping from Koop Star aboard a Garbage Pod, Mario, Luigi, Princess Toadstool and Toad crashed landed on the Mushroom Colonists' planet, where, after fighting off a Pokey and Cobrat, made it to the Mushroom Colony, where colonist Obi-Wan Toadi quickly devised a plan to penetrate Koop Star with Mushroom Starfighters. As Mario succeeded in blowing up Koop Star, the Mushroom Colony, along with the rest of the planet, was saved from the Birdo Ray.