There is no reason why you should take my word for this. Back in the days when ladies had a home journal (in 1918) the Ladies Home Journal wrote: “There has been a great diversity of opinion on the subject, but the generally accepted rule is pink for the boy and blue for the girl. The reason is 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.”The Sunday Sentinel in 1914 told American mothers: “If you like the color note on the little one’s garments, use pink for the boy and blue for the girl, if you are a follower of convention.” Some sources suggest it wasn’t until the 1940s that the modern gender associations of girly pink became universally accepted. Pink is, therefore, perhaps not biologically girly. Boys who were raised in pink frilly dresses went down mines and fought in World War 2. Clothing conventions do change over time.
still is in the UK
If the Ladies Home Journal said that in 1918 things must have changed a lot in the next 10 years, because I one of the earliest things I remember (even before starting in the first grade) was the Girls/pink, Boys/blue thing. The reason I remember that is because my mother for some reason thinking of buying me a pink shirt while we were shopping for my first grade clothes, and the first time I ever argued with my mother and got away with it (Dad was on my side) I told her flatly that I wouldn't wear it -- it was for sissies.
***jeeez, I don't think I've thought of that incident more that a dozen times in my life***