To modern eyes, this is surprising. “Pink is a girls’ color,” we think. This association has become so firmly entrenched in our cultural imagination that people are flabbergasted to learn that until the 1950s, pink was often considered a strong color and, therefore, was associated with boys.
See also, When Did Girls Start Wearing Pink? at the Smithsonian: http://www.smithsonianmag.com/arts-culture/When-Did-Girls-Start-Wearing-Pink.html
See on thesocietypages.org