Most people know that carrots have not always been orange. The original cultivars were purple, with some white and yellow mutations. So why is the modern carrot ubiquitously orange?
The orange strain was finally developed and stabilised by Dutch growers in the 16 - 17th centuries. A nice story has it that they were bred in the appropriately patriotic hue to honour William of Orange, the stadtholder of the United Provinces of the Netherlands.
Like many historical anecdotes, there is no documentary evidence to back this story. But it is a nice idea!