Despite their flag being composed of red, white and blue, the Dutch wear orange because it's the color of the Dutch Royal Family. The current Dutch dynasty is the House of Oranje-Nassau, which has a lineage that dates back to Willem van Oranje, whose name translates to William of Orange.
Orange in the Netherlands has become a symbol of national pride, which is why Dutch national teams frequently wear orange jerseys. Every year in the Netherlands, April 30 is Koninginnedag, or Queen's Day, a holiday celebrating the birth of the country's former queen. On this day, nearly the entire country will be dressed in orange.