I'm mid-cook on mine at the moment, and honestly it was a lovely shade of brown with the skin looking nice only about 2 hours in with just a little butter and some black pepper on the outside. I did brine it for 24 hours, which I've heard also helps. I just slathered a bunch more herb butter all over it so we'll see how it ends up.
Oh, fun fact, a 22 pound spatchcock turkey will just barely fit in my 3DW. Have to sort of squeeze the wings/thighs in and they may touch against the walls. Although, since they're so flat you could do at least two at once in there if you wanted to.