There are apparently three varieties: Sanguinello, Moro and Tarocco, all of which hail from Sicily, although the ones I bought this morning were grown in France. The red pigment develops in low winter temperatures, and contains more antioxidants that ordinary oranges.
There’s loads of wonderful recipes for using these but one of my favourites is Skye Gyngell’s Blood Oranges with warm honey and rosemary. All you do is put 130ml light honey and 3 tbsp water in a saucepan. Then add 3-4 sprigs of rosemary that you have bruised with a rolling pin to release the flavour. Warm gently over a low heat, taking care not to allow it to boil. Remove from the heat, allow to infuse for 10 minutes, then take out the rosemary. Remove the peel and pith from the oranges, slice into quarters and arrange on a plate. The pour over the infused honey and serve with vanilla ice cream.