The film was inspired by the real life friendship between Shirley, a pianist, and his driver Tony Vallelonga, who formed a bond during a tour of America's Deep South in 1962.
Amandla Stenberg, who was on stage with Lewis, then spoke directly about the "journey" characters take in the film, to which Lewis added: "Young or old, I encourage you to be an active participant in the journey - This is 'Green Book'".
The film also sparked controversy months ago when relatives of the pianist at the centre of the story, Don Shirley, complained his depiction in the movie contained inaccuracies.
Viewers had a mixed reaction to the surprise Best Picture win at the Oscars. "To depict him as less than, and to depict him and take away from him and make the story about a hero of a white man for this incredibly accomplished black man is insulting, at best".
"I got a call from Mahershala Ali, a very, very respectful phone call, from him personally. Always, always pushing me to think positively".
In the press room backstage, Lee recalled that a previous racial drama of his, "Do The Right Thing", had failed to earn a best picture nomination for the Oscars in 1989, the year that the film "Driving Miss Daisy" - about a black chauffeur for a white elderly Southern woman - won the award.
It was the second Oscar for the 45-year-old American actor, who took home the supporting actor trophy two years ago for playing a mentor to a young boy in best picture victor "Moonlight". Like really giving us space to work and tweak it out and coming in and tweaking.
The only other years that saw more than one actor of color winning at the same Oscar ceremony are 2007 (Forest Whitaker for The Last King of Scotland, Jennifer Hudson for Dreamgirls), 2005 (Jamie Foxx for Ray, Morgan Freeman for Million Dollar Baby), 2001 (Washington for Training Day, Halle Berry for Monster's Ball), and 1983 (Ben Kingsley for Gandhi, Louis Gossett Jr. for An Officer and a Gentleman). Accepting the original screenplay award for the film, co-writer Farrelly thanked "the entire state of Rhode Island", among many others.
"I can't believe they have John Lewis introducing Green Book", filmmaker Nia DaCosta tweeted.
Here is a glimpse of what people are saying on social media.
Remarkably, Cuarón's win for best director marks the fifth time a Mexican director has won that award in the past six years.
Not only that but during the acceptance speeches for Best Picture, Shirley himself was never thanked, nor was the man who created the actual Green Book.