Hi Scott,
I agree with Randy; the deck will look great with the color palette from the examples he gave. Almost all the posters from that time are lush in color, warm in tone, and high in contrast.
Also, I know it's going to take longer, but have you and Carlos considered having the artwork colored in by hand? Carlos' art for the deck is amazing, but you'll achieve more of a retro vibe if all the coloring was done by hand.