rhystic study mtg card Proxy The Gathering Rhystic Study (Confetti Foil)

As far as which Commander 2019 deck has the best colorless cards, it's somewhat subjective

They can be tutored with Open the Armory in an emergency, and enchant enemy creatures to take them out of combat

Since its also incredibly easy to leave mana up in a blue deck, and its so cheap for Meloku to bounce lands to your hand, its incredibly easy and safe to include Triskaidekaphile as an alternate win condition

Inalla lets you double up on those triggers by making a token copy of them for a single mana

However, Cavalier is much better than Grey Knight thanks to its ability to destroy any nonland permanent instead of just attacking creatures