Based on this funny yt video i found

You opened up cookie run: kingdom, seeing the devsisters logo except it was blue, thats weird.. the loading screen showed everything but blue and the title "Cookie run: kingdom" had been changed by "Shadow Milk: kingdom", you reloaded the game only to have the same problem.

When you went to get ur fountain rewards all of them were Shadow milk cookie, when u saw ur resources all of them were Shadow milk cookie except coins and diamonds which were Shadow milk cookie themed though.

You went and did some wishes which were normal, until a blue wish from pure vanilla cookie appeared and when you opened it, it was Shadow Milk cookie with a text bubble that said "wh-what?!" And the ressource to give was Shadow Milk cookie.

You went on the gacha which was normal. Until you pulled for cookies only to get Shadow Milk cookie.

You inhaled and let out a screech of anger