I always thought that the colors for pink and blue were something dreamed up by modern marketing agencies, maybe working for the Hallmark greeting card company. In recent weeks, stories have been circulating in the media that a new study "proves" that "girls prefer pink because they need to be better at hunting berries." See http://tinyurl.com/ypq48e for details.
"Hogwash!" says Ben Goldacre, author of the "Bad Science" column. He holds that the study is severely flawed and points out that our ancestors in the not-too-distant past reversed those colors. As the Ladies Home Journal wrote in 1918: "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."
Up until the 1930s, girls were typically dressed in blue and boys in pink. In fact, not too many years before that, little boys were often dressed in pink dresses! As Goldacre writes, "Boys who were raised in pink frilly dresses went down mines and fought in World War 2. Clothing conventions do change over time."
It is an interesting article that might give you just a slight glimpse into your ancestors' lives. Not only colors, but dresses for boys? (I do have family photographic evidence of this from about 1912.) He also provides links to some other articles on the topic.
You can read Ben Goldacre's "Bad Science" column at http://www.badscience.net/?p=518.
What did YOUR grandparents wear when they were young?