Link: https://scryfall.com/
Will be searching only for mono-colored cards of each on the date the question ends to see which color has the least cards. As of Dec 2023 the database shows the following:
White - 4083 cards
Black - 4046 cards
Red - 4013 cards
Blue - 3982 cards
Green - 3975 cards
1,000
3.00@marvingardens The only ambiguous one you listed is digital-only cards. I think you can safely assume playtest cards don't count, and split/adventures/multiple-printings each only count as a single card
@Tumbles You having an assumption on some set of them doesn't make them unambiguous... I certainly didn't know what your opinions would be. I think we need a set-in-stone search string from the market creator.
"how many magic cards are there" is quite far from a well-defined question. The people who work on scryfall would be the first to tell you that.
how about "Jadzi, Oracle of Arcavios." Will that show up for both the mono-green and mono-blue searches?