Painter's Servant says All cards that aren't on the battlefield, spells, and permanents are the chosen color in addition to their other colors.
Further clarified by the ruling: This ability affects every card in every game zone, all tokens on the battlefield, and all spell copies on the stack, regardless of who controls or owns them.

Does the Undercity dungeon become colored because of Painter's Servant?


Painter's Servant says all "cards"
108.2 says when a rule or text on a card refers to a “card,” it means only a Magic card or an object represented by a Magic card.
108.2a says there are traditional magic cards and nontraditional magic cards, but doesn't specify any as not being Magic cards.
Further, 108.2b does specify that tokens are not cards, even if there are card-like representation of them.
So just because a card is nontraditional does not stop it from being a Magic card.

309 is the section dealing with dungeons. Here we learn via 309.1 that Dungeon cards are a nontraditional card (still a card through 108.2a) & 309.2b that Dungeon cards exist in the Command Zone (a game zone through 408.1)

I see no reason why Painter's Servant naming blue would not color the Undercity blue, making cards like Veil of Summer interactive with target effects like Trap or Arena.

Thoughts and feedback appreciated.
Thanks