9 cards where the card is tagged “color-count-matters”

A-Paragon of Modernity (Streets of New Capenna #A-242)
Evolving Door (Streets of New Capenna #144)
Invasion of Ravnica // Guildpact Paragon (March of the Machine #1)
Invasion of Ravnica // Guildpact Paragon (March of the Machine #1)
Meeting of the Five (Streets of New Capenna #202)
Niv-Mizzet, Guildpact (Murders at Karlov Manor #220)
Niv-Mizzet Reborn (War of the Spark #208)
Niv-Mizzet, Supreme (March of the Machine: The Aftermath #40)
Paragon of Modernity (Streets of New Capenna #242)
Threefold Signal (New Capenna Commander #93)

Their mind whirled with grand plans, never thinking of what might happen if they got to the end of the list.