[bluGill]

That is most common, but a tiny minority see no colors.

[dmd]

One in 40,000. Being completely blind is VASTLY more common.

[MaxPengwing]

So that's still somewhere between 6600 to 11000 people in the US alone. Assuming a range of 1/300000 to 1/400000 out of 331 million US Citizens...

So while rare, its not impossible to run in to.