Bring a medium pot of water to a boil and drop the white sweet potatoes in. Lower heat to a low boil and cook until sweet potatoes are tender, about 15 minutes, exact time depending on the size of your pieces. When the sweet potato can be very easily pierced with a fork, turn down the heat all the way, remove the sweet potatoes from the water with a slotted spoon to a colander to drain.

Turn the heat back up to bring the water to a boil. Add the orange sweet potato to the boiling water, reduce heat to a low boil, and cook until sweet potatoes are tender, about 15 minutes, exact time depending on the size of your pieces.

While the orange sweet potato are cooking, put the drained white sweet potatoes in a food processor and pulse. Add 1 tablespoon butter, about ½ teaspoon salt, and some of the cooking water from the pot to food processor while you pulse until a smooth puree forms. Remove white sweet potato puree from the food processor to a bowl. Wipe out the bowl of the food processor or rinse it.

When the orange sweet potatoes are tender, remove from the pot with a slotted spoon to a colander to drain. If the cooking water is not too tinted or has a lot of small broken pieces of orange sweet potato, use the same water to cook the purple sweet potatoes. Otherwise, save about ¼ of the cooking water, dump the rest in the pot, and bring a pot of fresh water to a boil. Add the purple sweet potatoes, lower heat to a low boil and cook until sweet potatoes are tender, about 15 minutes, exact time depending on the size of your pieces.

While the purple sweet potatoes are cooking, put the drained orange sweet potatoes in the food processor and pulse. Add 1 tablespoon olive oil, about ½ teaspoon salt, and some of the reserved cooking water from the pot to food processor while you pulse until a smooth puree forms. Remove orange sweet potato puree from the food processor to another bowl. Wipe out the bowl of the food processor or rinse it.

When the purple sweet potatoes are tender, reserve ¼ cup of the cooking water, then drain them in a colander. Put the cooked purple sweet potatoes in the food processor and pulse. Add 1 tablespoon butter, about ½ teaspoon salt, and some of the cooking water from the pot to food processor while you pulse until a smooth puree forms. Remove purple sweet potato puree from the food processor to another bowl.

Transfer the whipped sweet potatoes to a serving dish, keeping each color separate from the others as much as possible. Top the white sweet potatoes with 2 tablespoons of room temperature butter and sprinkle with chopped fresh herbs. Top the orange sweet potatoes with Whipped Feta and Pomegranate Salsa. Top the whipped purple sweet potatoes with blue cheese and toasted walnuts.