Mutons were an indigenous humanoid species from the planet Muton with greenish-blue skin.
History
In the 2260s, frogmen from the Salgorax-Neptor system invaded Muton, slaughtering a majority of the natives. Survivors were kept in slavery.
In 2265, freedom fighter Dalbar led a rebellion against the frogmen. He managed to drive them out of the capital city and free the natives that had been enslaved there. He looked forward to his people continuing and finishing their fight. (TOS comic: "Slaves of the Frogmen")