Here's a link to a post from Sep 2015 asking a similar question:

https://www.reddit.com/r/AskHistorians/comments/3kopmb/where_did_the_association_of_pink_for_girls_and/

From April 2015:

https://www.reddit.com/r/AskHistorians/comments/32pfdh/why_did_the_colors_associated_with_each_gender/

Also, a somewhat related question from Oct 2017:

https://www.reddit.com/r/AskHistorians/comments/75855k/wheres_the_evidence_that_pink_was_once_a_color/

Also, from Sep 2018:

https://www.reddit.com/r/AskHistorians/comments/9h6mcg/when_did_blue_become_a_boys_color_and_when_did/

This one from Oct 2013:

https://www.reddit.com/r/AskHistorians/comments/1nyulx/how_did_blue_become_the_boy_colour_and_pink/

Okay, I'm gonna stop there.