Scuttlemutt — ruling 1

You must choose one or more of the five colors of Magic while resolving Scuttlemutt’s last ability. You can’t choose “artifact,” “colorless,” or “chartreuse.”

Scuttlemutt — ruling 2

The target creature has only the colors Scuttlemutt gives it—Scuttlemutt’s ability overwrites any previous colors the creature had.

Scuttlemutt — ruling 3

In the Commander variant, the color identities of cards are determined as the game begins. Changing the colors of a player’s commander doesn’t affect its color identity or the cards that can be legally included in the deck.

Scuttlemutt : règles, fonctionnement et interactions (MTG)

Scuttlemutt is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

: Add one mana of any color. : Target creature becomes the color or colors of your choice until end of turn.

How it works : Scuttlemutt

Original English text — Wizards of the Coast / Scryfall

#1July 12, 2019· Wizards of the Coast
You must choose one or more of the five colors of Magic while resolving Scuttlemutt’s last ability. You can’t choose “artifact,” “colorless,” or “chartreuse.”
No other card is named in this ruling.
#2July 12, 2019· Wizards of the Coast
The target creature has only the colors Scuttlemutt gives it—Scuttlemutt’s ability overwrites any previous colors the creature had.
No other card is named in this ruling.
#3July 12, 2019· Wizards of the Coast
In the Commander variant, the color identities of cards are determined as the game begins. Changing the colors of a player’s commander doesn’t affect its color identity or the cards that can be legally included in the deck.
No other card is named in this ruling.