According to one website, it originated in Denmark. According to another it was the Netherlands. According to Wikipedia, it originated in Italy. But from my research, it seems the first and only true purple cauliflower is the Purple Cape Cauliflower, an heirloom variety that came from South Africa in 1808. Since then there have been a few hybrids. One is Violet Queen, a cross with a purple variety of broccoli. 
Then there is Graffiti, a hybrid (I suspect with Purple Cape) This one is reported to be sweeter and nuttier than white cauliflower, and even retains its color when cooked! (color stays better if a tsp. of lemon juice is added to cooking water)I think I will try both Cape and Graffiti in my garden.
The purple color is due to formation of anthocyanins also found in red cabbage and in red wine. Anthocyanins are healthy compounds belonging to the group of phenolic antioxidants. This is one reason why many doctors recommend drinking a glass of red wine every day.
