Cook the sweet potatoes and potatoes in a saucepan of boiling water for 15 minutes, then remove and drain. Put the sweet potatoes in a bowl and the potatoes in a separate bowl.
Mash sweet potatoes and potatoes until light and fluffy, gradually adding half of the cream cheese and half of the milk to each, the same with the BBQ sauce.
Add the bacon and brown sugar to the mashed sweet potatoes and stir; add the chopped green onion to the mashed potatoes and stir.
Mix both purees so they come together. You can mix them completely or in a swirl so that both colors show.