If you'd like to use these with HDRP in unity, this thread contains a link for an unlit shader: https://forum.unity.com/threads/is-there-an-hdrp-version-of-a-vertex-color-shade...
After a little bit of messing around, I was able to get this lit shader working as well: https://www.dropbox.com/s/j6ickmm8ibz6xl6/LitVertexColor.mat?dl=0
