came home with White Sweet potatoes. How can I make them orange for thanksgiving

No hope on the color unless you call Harry Potter for a magic spell.
They still taste good!

Unless you really need them to be orange in color, white sweet potatoes can make a darn fine sweet potato casserole too! If you're more concerned about the color, though, you could add some mashed carrot, butternut squash, or pumpkin.

You could dye them I suppose, but they're vastly different in taste aand other characteristics- I'd go back to the store.