Mel Ramos’s paintings and prints of 1950s-era pin-up girls—variously popping out of Snickers bars, leaning on packets of Lucky Strike or caressing giant Coca Cola bottles—offer a humorous, overblown take on that age-old advertising adage: sex sells. The West Coast counterpart to Manhattan’s Warhol and Lichtenstein, Ramos was among the artists that defined pop art in the 1960s.