This evening's thread is going to be about the idea that "boys used to dress in pink and girls in blue, but then that switched for important symbolic/historic reasons," which is completely untrue yet very popular on the internet.
Major h/t to @jbpaoletti, who literally wrote the book: https://www.amazon.com/Pink-Blue-Telling-Girls-America-ebook/dp/B007A0PHL0
So yeah. This is a very popular factoid, frequently presented as a kind of Today I Learned or BUCKLE UP subject. Which is generally a good indicator that something's not quite on target.
If we go back to the 18th or 19th centuries, we can see very easily that there is NO assignment of pink or blue to anyone. Infants and toddlers were typically dressed in white across the board, and accessory/trim colors were no signal as to gender.
Once old enough to be dressed in colors, there was no rigid ideology relating color to gender. The two below are both boys! Louis XV is on the left and James Badger on the right. Louis is more fashionable and fancy because he's much richer.
In the late 19th/early 20th centuries, you were a lot more likely to see colors assigned by the baby's hair color. Pink was said to go with blond hair and blue with brown. (But still, not necessarily universal.)
In the 1910s and 1920s, magazines and department stores started recommending pink and blue as gendered colors. But ... they don't agree. Some say pink-girls/blue-boys, some say the opposite.
Because there was no standardization, it wasn't odd at all for a baby boy to have pink clothing and bedding, or to have a mix of colors, or for a girl to be dressed in blue, even though some stores would have said that was "wrong".
But there also wasn't a tradition of pink being an inherently masculine color because it was a lighter version of red, or of blue being inherently feminine because it was associated with the Virgin Mary. There wasn't a "switch".
The idea that pink was for girls and blue for boys was pretty set in stone by the 1950s, but it still wasn't really important. That would happen in the 1980s, ie the infancy/childhood of many Millennials.
From around 1965 to around 1985, pastels and gendered colors went out of style for kids. Instead, parents reacted to their own gendered childhoods and chose bolder colors and more unisex styles (particularly liberal parents).
The pendulum swung back - and then some. In the end, the idea that girls and boys MUST wear particular colors (and the ensuing intense gendered marketing) is actually quite recent.