What kind of veggies and fruits can a green iguana eat.. Also why did he turn dark green????

I was just wondering what kinda fruits and veggies my iguana can eat and what should his every day diet be made of.. and also I only got him 2-3 day ago but today when I held him i relalized that he turned a dark green... anyone have any reason why this could be happening, if its just the new envoirment and feed or is it stress... he seem healthy.. soo I need Help...