in 1918 the trade publication Earnshaw's Infants' Department stated that "pink, being a more decided and stronger color, is more suitable for the boy, while blue, which is more delicate and dainty is prettier for the girl." During the 1940's many retailers realized a shift in the preferences of parents and navy became the more masculine shade. Before long pink was considered more "girlie."
As my granddaughter once said when she was quite young: "Pink is for girls." Captain Kirk of the U.S. Enterprise would say: "Let it be so."