Cut each potato into 4 portions, lengthwise.
Mix the milk with the water in a pot, add the cumin, salt, pepper and the color.
Add the potatoes and cook over medium heat for about 10 minutes, add the butter and continue cooking for about 5 minutes more or until tender, but firm.
Place the cooked potatoes in a serving dish with the sauce and sprinkle the grated cheese on top. You can place the potatoes under the broiler for a couple of minutes if you prefer the cheese to be melted. Serve immediately.