The actor shared a heartbreaking tribute to Olivia on social media shortly after her death was announced on Monday.
On Tuesday, Richard Wilkins, Australia's Nine entertainment editor, appeared on Good Morning Britain, revealing that he had spoken to John via text message.
VIDEO: Grease star Dame Olivia Newton-John dies aged 73
He said that the actor was "too raw to talk" and understandably devastated by the news.
He also said that Olivia was a "beautiful, warm, loving person," and that she "just radiated goodness."
He added: "She was there for everybody all the time. She was so generous... here in Australia we just loved her. It was always 'our' Olivia. She was just a good person, she was immensely proud of her achievements... she was a dame, she had four Grammys... but at the core of it all she was just a good person."
Richard was a long-time friend of Olivia and broke down in tears on Monday's Today Show in Australia.
John Travolta is "too raw to talk" following the sad news of Olivia Newton-John's death
Host Karl Stefanovic left his seat to comfort his colleague, telling him: "Oh buddy. Well done there. Your relationship with her was so beautiful." "I don't want to do this," Richard said as he grabbed a handful of tissues.
"It's alright," Karl said, giving his co-star a hug. "She touched everyone, didn't she? Even through a Zoom call, whether it was someone in a hospital, someone on the boardwalks of Hollywood who didn't even know her that well, that depth of feeling, this woman was extraordinary."
"Well, I'm still numb," Richard said. "I've got nothing more to say."
John had led the tributes to Olivia after her death was announced by her husband John Easterling.
John and Olivia remained great friends following Grease
He shared a gorgeous throwback photo of his friend, alongside the message: "My dearest Olivia, you made all of our lives so much better. Your impact was incredible. I love you so much.
"We will see you down the road and we will all be together again. Yours from the first moment I saw you and forever! Your Danny, your John!"
Read more HELLO! US stories here
Like this story? Sign up to our HELLO! Mail newsletter to get other stories like this delivered straight to your inbox.