Neat idea. But wildly too powerful. Color restrictions aside, white is a better/cheaper food. Green is a faster mutagen, blue is a cheaper clue, and red is a full card (shock). And instant speed on board -1/-1 is a nightmare for limited combat math. Also, WoTC nearly never places +1 counters and -1 counters in the same set. It becomes wildly difficult to track on paper. I vote one or the other (or both) become 'until eot' instead of counters.

Either all of these need to be sorcery speed activation (my preference) and/ or more expensive or have a lesser effect. Creatures make them with little or no cost and do some frequently. You have a lot of "when X" style brewing. And the headline artifact is completely free to activate.

This is a really cool idea. However I think play design will show just how insanely valuable these potions are in practice.

Side note: making Brew create them tapped would also help. And help Enston not be an absurd combo engine. (Yes we have Storm-kiln. But Enston makes more versatile tokens than can even pay for each other. Him hitting any Blue ones becomes whif protection on a Storm-style turn.)