Blood orange is a citrus fruit with crimson-colored flesh on the interior that looks like a typical orange on the outside. It gets its lovely red color from an anthocyanin pigment, which only appears when low night temperatures. Because anthocyanin develops first along with the peel and margins before moving interior, some blood oranges are streaked with crimson rather than solid red. The pigment also gives raspberries and blackberries their color. Blood oranges are thought to have originated in the southern Mediterranean.