White: Easily the richest color (at common) for +1/+1 counters along with green. part of the reason the cube took as long as it did. I think This color has the most room for tweaking.

Blue: This was actually very short for on theme cards at common. Was the exact opposite of white. I was glad to get a few cards out of NEO. It still has a few generic cards to round the count. I opted for primarily instants to pair with the two pyro grow creatures in red to make a link between the two.

Black - Black ventures into -1/-1 counters as a foil/ balance for the counter growth. There is also a small Unearth subtheme due to one of the WB cards.

Red - Red has a lot of deal damage get counter cards, but I didn't want to get so aggro it imbalanced the colors. I linked it with U a bit thanks to Pyre Hound and Pyroceratops. I also made sure to include a few more 'big' burn effects like 4 to creature because shocks will not do well against a counters theme.

Green - Green needed no assistance to be a strong +1/+1 counters color. I opted for only one of the 3 (I think) trample for +1/+1 counters creatures. I didn't want green to be super unblockable. I was also glad to see that a lot of fight effects relate to counters as well.

Multicolor - I didn't want to be imbalanced on color count, but some colors really lacked counters cards at common (Simic cards for counters were apparently largely uncommon+) This is where I got into the subtheming. Breathless Knight encouraged some Unearth in WB. Dramatic Rescue and Turn to Mist created a bit of a blink/bounce theme, which is nice to also reset opposing creatures or save your own. The UR ones lean into the spells theme.

Lands - Simple fixing, two tapland cycles. I opted for the Gainlands and Snow basics. They were recent, so I was happy to use them Also with Gainlands in NEO the art is fantastic. I did consider mana rocks of some kind, but it would eat a lot of space in a very small cube. Considerations: Diamonds cycle or Borderposts. Why even consider rocks at that point? Might be right on that one.