The symbolism of the orange was a long running kind of inside joke among FFC and his crew. You can read about this in some detail in "The Godfather Legacy" by Harlan Lebo.
As posted on Don Malta's GF Trilogy Website:
The first time we see Sal, he tosses himself an orange at Connie's wedding. He later betrays Michael... Bye bye!
There's a fruit basket with oranges in front of Sandra as she gestures to others the size of her husband Sonny's manhood
There's a bowl of oranges in front of Woltz. We know what happens to his horse!
There are oranges around when Sollozzo enters the Don's office for the meeting. Dead man!
Right before he was shot, Don Corleone bought 2 oranges! Oh, man... an omen!
And as he topples to the street, the Don upsets a basket of oranges into the street!
When sitting with his father after he returns home from the hospital, Fredo sits next to a fruit basket of oranges. He later betrays the Family and his prayers cannot help him!
At the commission meeting of the Five Families, bowls of oranges are placed in front of the Don, Philip Tattaglia and Barzini. Ciao!
What does Don Vito have in his mouth moments before he dies? Yup!
Not fruit, but... Carlo gets his ass whipped by Sonny, while wearing an orange suit.
Not fruit, but... Kay wears an orange coat when she comes looking for Michael at the compound.
Not fruit, but... Michael's tie when he talks with Moe? orange!
Not fruit, but... More orange clothing: Masseuse's pants, Woman behind Barzini fall on steps, Assassin's shirt at revolving door...!
Don Cardi
