Pink was considered a masculine colour 100 years ago, and blue was feminine.

Reference: " In the early 1900s, The Women's Journal wrote that pink was a "more decided and stronger colour" that was best suited for boys. According to the Journal, blue, was "more delicate and dainty" and better for girls. " http://www.cbc.ca/thecurrent/2009/200901/20090128.html

The original radio broadcast is available online.