For centuries, children wore dainty white dresses up to age 6. (…) The march toward gender-specific clothes was neither linear nor rapid. Pink and blue arrived, along with other pastels, as colors for babies in the mid-19th century, yet the two colors were not promoted as gender signifiers until just before World War I—and even then, it took time for popular culture to sort things out.

cely clanok: http://www.smithsonianmag.com/arts-culture/When-Did-Girls-Start-Wearing-Pink.html