If I search with the following criteria https://deckbox.org/sets/3031565?f=796!p4MA**&s=i&o=d:
Color Exclusively one of colorless
Number of Colors Equals 0
(this returns about 85% of the colorless cards on my trade list)

I get a set of cards that is mutually exclusive with the cards returned by this search https://deckbox.org/sets/3031565?f=796!p4MQ**&s=i&o=d:
Color Exclusively one of colorless
Number of Colors Equals 1
(this returns about 15% of the colorless cards on my trade list - this includes Horn of Gondor as an example of a relevant affected card)

Hey there,

I think putting together two limits that are similar but kind of contradictory:

Color - Exclusively one of colorless
Number of Colors - Equals 1

This sounds like is both colorless and also of a color (number equals 1)

Perhaps a better point of where this is weird:

Number of colors = 0 - 193 Results
Color = All of Colorless - 227 Results

I could not find consistency in why is one and not the other:
Argivian Avenger
Clown Extruder
Ent-Draught Basin

So while I don't have an answer, I think removing the stacked criteria might help diagnose

Not sure if it will help in this case but the colorless filter will only pull cards that have no color identity. For example, the talismans and signets are all colorless mana rocks but have each of the 10 color identities (Azorius, Boros, etc.) and will only appear if those colors are selected in the filters.

Same goes for any other cards where the card itself is one color but has a different colored mana symbols on the card. Elves of Deep Shadow won't show up when filtering for green cards (since the color identity is actually Golgari).