Astrid, on this delicious-looking card, explains that these confections, called "beschuit met muisjes" are traditionally made to celebrate the arrival of a baby.
Naturally, girls are celebrated with pink "muisjes" and boys with blue ones. Or is it "natural"?
Astrid's question is "Why is it pink for girls and blue for boys?"
I turned to the clarifier of all things obscure: Cecil Adams of the Straight Dope website. Here's the link: