Herndon and Collum, who have been dating for five years, walked the red carpet together outside the Hollywood Palladium, where Herndon was set to appear as part of The Trevor Project's annual charity event.
The 52-year-old "It Must Be Love" singer and his partner were all smiles as they stayed close while posing for photos on the red carpet.
The Trevor Project is a non-profit organization that provides counseling, crisis intervention and suicide prevention services for LGBT youth.
At TrevorLIVE 2014, the organization's annual charity event, Herndon, Glee star Darren Criss and 2 Broke Girls actress Jennifer Coolidge were among the celebrities who lent their star power to the event.
In his November interview with ET's Nischelle Turner, Herndon opened up about Collum, saying, "I have an awesome relationship that I've been in for a good number of years… [I] love him very much and he loves me."
Herndon, who has been married twice before, also revealed that his ex-wives, and a number of close friends, knew about his sexuality long before he came out.
"I had a lot of people around me that I trusted at a time and I was like, 'Hey, you know this about me but the world doesn't.' So I'm gonna need to call on your services for a little while," Herndon told ET. "It was unfortunate that I had to do that, but I felt that's what I had to do to have my career. [I'm] standing on some pretty solid legs today, so I get to tell my truth today."