Metaballs are different colors in sculpt mode I created a few metaballs and used boolean to combine them with another mesh.

The dark purple is what were the metaballs. They are one object, but a different color from the fingers I connected to them. Already checked the normals, they're all flipped outside. And there are no materials.
I had the same issue, try turning on (Dyntopo) it worked for me.
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