Any support card giving +1/+1 counters to Skullbriar, the Walking Grave is a worthwhile consideration
By now, there are swaths of cards across the other four colors that can be playable in an artifact deck

Julius Jumblemorph Dragonlord Dromoka Drizzt Do'Urden Dromoka, the Eternal Dyadrine, Synthesis Amalgam Ellivere of the Wild Court Emmara Tandris Emmara, Soul of the Accord Farmer Cotton Finneas, Ace Archer Frodo Baggins Gabriel Angelfire Gaddock Teeg Garnet, Princess of Alexandria Ghalta and Mavren Gluntch, the Bestower Gylwain, Casting Director Haliya, Ascendant Cadet Hamza, Guardian of Arashin Janai and Hoppy, Roofskippers Jasmine Boreal Jasmine Boreal of the Seven Jenson Carthalion, Druid Exile Kaheera, the Orphanguard Karametra, God of Harvests Katilda, Dawnhart Prime Kei Takahashi King Darien XLVIII Krond the Dawn-Clad Kudo, King Among Bears Kutzil, Malamet Exemplar Kyler, Sigardian Emissary Lady Caleria Lagorin, Soul of Alacria Lathiel, the Bounteous Dawn Leinore, Autumn Sovereign Lord Magnus Maja, Bretagard Protector Mary Jane Watson Melira, the Living Cure Merry, Warden of Isengard Mikey & Leo, Chaos & Order Miriam, Herd Whisperer Mirri, Weatherlight Duelist Ms

Its especially strong in metas with lots of counterspell-heavy control
These cards didnt permanently change colors though