I love holographic nail varnish!
This is the only one I own, and it's made by Seventeen, which I think is only available at Boots. It's the only holographic shade they have, and was brand new when I got it two years ago, so I'm not 100% sure if they still make it
It looks its absolute best when you shine a light on it, so I took a photo with flash to try and show that. The light really catches all the bits of glitter and shows an almost rainbow effect, but you can't quite see it in the photos.
Seventeen is a really affordable brand, and their nail polishes vary from £2.99 to £3.99, so I would have paid somewhere between those prices. The only downside is that I do find it chips and tarnishes quite easily. I don't know if that's just for this particular colour/effect because I've never tried any of their other nail varnishes.
I applied Maybelline Super Stay base coat, two coats of the Holo Silver, and one coat of Revlon Gel Envy Diamond Top Coat.