Hey, thanks for the post.
Yeah, the green is made by the yellow overprinting the blue. I love messing with overprinted spot colors. See our Five Dollar Foundation, Superdrag, Low, Volante.
mother fuck this is a fine poster. I keep coming back to it just to admire the shape of the blue space. I'd love to know if that green is process y + cyan...
In any case, it's often on my mind. Well done.