Kevin is the most recurring person of color on Supernatural with 17 episodes.
Billie follows up with 15. Other characters are Rufus with 6 (+2 just voice), Kaia and Raphael with 5, Victor Henriksen and Gordon Walker with 4, Patience and Dagon with 3. Linda appears in 5 episodes, but is played by two actresses. Kelly also appears in 7 episodes but it’s not clear if she’s a person of color in narrative as she’s light skinned and her parents are portrayed by white actors.
Mary is the most recurring female character, with 39 episodes.
Rowena follows up with 33 episodes. Ruby, Amara, and Jody come in with 17. Billie once again appearing with her 15. Meg with 12 (+2 Shadow appearances). Lisa with 11. Ellen, Abaddon, and Naomi with 9. Jo Harvelle, Kelly, Charlie, and Donna with 7.
LGBT characters are highly debated right now so I’m going by the Superwiki’s list of LGBT+ characters. Cas has over 100 episodes, but only a few where his gender or sexuality is mentioned. Michael/Adam, Crowley, Billie, Jack, and Dean were all portrayed as being LGBT+ by their actors but there are ongoing debates over this. Jared said that Sam might be LGBT but he never thought about it. Rowena was implied to be bisexual in a cut scene. Chuck is in 19 episodes, and his bisexuality is mentioned in 1. Charlie has 7 episodes (+4 AU Charlies) and is out from her first episode. Claire is in 7 but isn’t out until after her last appearance. Max appears in two episodes as a LGBT man of color until he is entirely forgotten. Max and Stacey appear in two episodes. There are many LGBT+ characters in stand alone episodes like Lily Baker, Ceasar and Jesse, and Corbett.
In total, the series had over 300 episodes. While I do want to point out episode counts, I’d like to mention that quality is more important than quantity. Eileen is a well loved and remembered character because of her character and her actress, and she was treated well (edit: Aside from Bucklemm). Kevin, however, was written with a ton of stereotypes, and then as he evolved out of them, he was mistreated by other characters and often put in horrible situations beyond what the other characters were being treated as. Also to note, a lot of Mary’s original episodes are flashbacks or AUs or illusions for man pain. Mary is a good character but a lot of the episodes she appears in don’t serve her well. Also, note the antagonists and how they were portrayed.
You can still absolutely love what SPN was without ignoring this. I saw an asian american fan writing about how she stopped participating in fandom because people said she was crazy for pointing out how asian americans were treated on the show. Believe people. Listen to them.