They will ripen at room temperature.
They will turn an orangish color.
Once they are ripe, bag and freeze them or they will spoil quickly. I suspect thats why the supplier sent them to you green.
Personally, I would not feed green palm fruit to my Grey. As I said in my other post, they contain nuerotoxins. If you watch birds in the wild, they never eat unripened fruit, including Palm Fruit. I have wtached several queen palms around my neighborhood and the birds feed on them when ripe.
I feed my Grey 2 to 3 palm nuts 3x a week.
I limit them due to the Red Palm Oil I mix in with his foods.