Ghostfire Slice

• WWizards of the Coast2024-06-07
  Official Ruling
  Other cards and abilities can give a card with devoid a color. If that happens, it's just the new color, not that color and colorless.
• WWizards of the Coast2024-06-07
  Official Ruling
  Devoid doesn't affect the color identity of the card for the purposes of the Commander variant. For example, while Abstruse Appropriation is colorless because it has devoid, its color identity is still white and black, and it can't be included in a Commander deck where the commander's color identity doesn't include both white and black.
• WWizards of the Coast2024-06-07
  Official Ruling
  Devoid works in all zones, not just on the battlefield.
• WWizards of the Coast2024-06-07
  Official Ruling
  If a card loses devoid, it will still be colorless. This is because effects that change an object's color (like the one created by devoid) are considered before the object loses devoid.
• WWizards of the Coast2024-06-07
  Official Ruling
  A card with devoid is just colorless. It's not colorless and the colors of mana in its mana cost.

Rulings via Scryfall