The song isn't off beat but the performance certainly is. In 1970, Kermit the Frog performed Being Green on Sesame Street. 1970! Geez, I was the ripe old age of 18. I hadn't realized Sesame Street had been around that long. I think Kermit might be older than I am!
Now, I was too old for Sesame Street so I first came across this song on the album Hard Nose the Highway by Van Morrison - a great album by the way - and for years I thought he wrote and was the first to perform the song.
Turns out, the song was written by Joe Raposo specifically for Kermit's character, as performed by Jim Henson, in the first season of the ground-breaking children's television show. The song was meant to teach children to be happy with themselves, starting out with Kermit lamenting his greenness but by the end of the song he's quite comfortable with it, singing "It's beautiful! And it's what I want to be..."
And Van Morrison wasn't the first artist to cover the song. That distinction goes to Frank "It's Not Easy Being Chairman of the Board" Sinatra on the 1970 LP Sinatra & Company.