Because it was forced. If you had acceptes that pink crayons were for girls and blue is for boys, then you are agreeing to shut all blue things out of your life, as not being for you. Like, the sky, the ocean, all things associated or often marketed with blue, like tech, sports, etc.

Then it'll be that all things that go into "blue space" are not for you either. Like birds, dolphins, computer games, airplanes, etc.

That's kinda stark, but that is the level of thinking at that age.

That's why you rejected pink. You were rejecting a rigid straightjacket version of seeing the world and how you're allowed to live in it.