Sally Hansen - Hard as Nails - Xtreme wear - 25 Night Lights
It may be not a grey holo, but it looks like one in artificial light, i guess.
In daylight too, but it was difficult to catch it on camera.
In general, very nice polish.
However, it's a bit difficult to remove, cause it contains glitter.
What's more, you need to apply 3-4 coats to achieve the effect in the photos.
But it dries fast, so it's not a problem.