Enchant creature.

When Nephe Shaddoll Fusion enters the battlefield, choose a color.

Enchanted creature becomes the chosen color in addition to its other colors.

{1}{U}{B}: Fuse Shaddoll. (Send creatures from your hand and/or from the battlefield under your control to the graveyard, including the enchanted creature. Place one Fused Construct creature with Shaddoll in its name that can be made with the sent creatures from your Extra Deck on the battlefield tapped.)