"Beautiful, beautiful guy. I don't even know how to talk about it," Quinto told Colbert. "You know, we already knew this was going to be a bittersweet experience as a result of the loss of Leonard [Nimoy] last year, but this has been absolutely devastating for all of us."
"I think our goal just has to be to celebrate his incredible life and honor him as much as we can," he explained. "It was a terrible loss, not only to us, personally, but to the industry and to audiences. He was such a talent."
Yelchin unexpectedly died on June 19 -- the actor was struck by his car and pinned to a security fence in the driveway of his Los Angeles home.
As Quinto noted, his relationship with Yelchin became extremely close over the past nine years shooting the Star Trek films, and while he said the bond he shares with the sci-fi franchise's cast is close, he also admitted it is something they "take for granted." "We genuinely love each other so much…but we are truly intertwined inextricably, and I think we always will be," he said.
Watch Quinto's interview in the video below:
Several of Yelchin's other co-stars have also opened up recently, sharing thoughtful tributes to the late actor.
Zoe Saldana took to Instagram last week to share her thoughts on the devastating loss.
"Your sudden and unexpected departure has left us all broken hearted," the 38-year-old actress wrote. "I woke up today feeling absolute gratitude that I had you as a friend and colleague."
"Your life has been cut short, but I will always tell everyone about you…Goodbye Anton, it was an honor to have crossed paths with you," she said.