In a small heatproof bowl, crumble the saffron into the boiling water. In a large saucepan, combine the cold water with the rice and bring to a boil. Cover and cook over low heat until the water is absorbed and the rice is tender, about 17 minutes. Fluff the rice with a fork.
Transfer 1 cup of the cooked rice to the bowl of saffron water and stir until the rice is yellow. Spoon the white rice into a large shallow bowl, top with the saffron rice and serve at once.