With
Whim of Volrath, player A changes a color word on a permanent from X to Y until end of turn. During the same turn, player B changes the new word on the same permanent with
Sleight of Mind from Y to Z. That effect lasts indefinitely, but is it still applicable after the current turn?
My guess: The color word on the permanent is X again after the effect from
Whim of Volrath wears off, so an effect trying to change Y to Z does nothing, and it's X.
Thanks,
Mario Haßler