Vertex colors are being stripped after build

First of all, my meshes have assigned vertex colors from external software, and the only thing that doesn't work is loading vertex colors. Vertices and everything load correctly. I am loading my mesh using "Resources.Load". It works in editor, but after build "mesh.GetColors" returns empty list of colors. Is unity stripping my vertex colors? How can I prevent it? *Happens both in il2cpp and mono build