It would still be VMC even if you are on instruments.
I remember this point was made to me by a FI when I did my NVFR. Pitch black night no horizon. Me flying on instruments asking if I could log it as IF. No was the answer, because you are in VMC (clear of cloud 10k viz etc). Funy thing about it was later in life I was flying under the same conditions (except on an IFR plan) and flew into some cloud. The only deiiference was that the strobes started to reflect back into the cockpit.