From These Are The Voyages: TOS Season 1 by Marc Cushman and Susan Osborn (2013):
The African-Canadian actor Percy Rodrigues was hired to play Commodore Stone. Rodrigues had a commanding presence on the small screen and often found roles that were unique and inspiring for black viewers. He played a doctor on Ben Casey, a Sheriff on The Fugitive, an African leader on The Man from U.N.C.L.E., a debonair assassin on The Wild, Wild West, and now Commodore Stone, a starbase commander.
And I found this additional info in his IMDB bio:
A symbol of intelligence, leadership and moral strength in his various 60s and 70s roles, African-Canadian actor Percy Rodrigues rose in Hollywood stature during the late 60s following a couple of earlier Broadway appearances. The serenely handsome, distinguished-looking actor also became notable for helping to break racial barriers on TV and went on to become a voice of great distinction behind the camera.
The oldest of four children born to a Montreal couple on June 13, 1918 (some references list 1924 as his birth year), Percy was of African and Portuguese descent. His father abandoned the family while he was a youth and Percy started working as a teenager to help provide for his family. By his late teens he had become a professional boxer and started scouting out acting jobs at the same time. He joined Montreal’s Negro Theater Guild and although winning a Canadian Drama Festival acting award in 1939, found job offers scarce, prompting him to work as a machinist and toolmaker for the next decade or so in order to supplement his income.
After narrating some Canadian documentary shorts and appearing in some Broadway roles, he moved to TV and film work in Hollywood, including Star Trek. After about two decades of acting these kinds of ground-breaking roles he decided to move back into voice-over work. He passed away in 2007 at the age of 89.