One of the nail polishes I got for Christmas was Layla Hologram Effect in "Mercury Twilight", a sparkly silver with a strong holo. I looked through pics of many silver holos to choose my favorite & have wanted this one for a while.
Unfortunately under most lighting you get a faint rainbow flash. You can barely see it on the middle nail here ~
Under bright lights & in the sunshine you get a much stronger rainbow. It was cloudy all week so I couldn't test out the sun, but it did look lovely under the bright light in our shower.
Holos are hard to capture, so you'll have to trust me that it was a lot more like the middle nail above. (Or do a Google search to see how pretty it can be)
Wear time ~
Holos are known to chip easily - I was a little worried when I saw one girl complaining hers began chippping after 3 hours! But you just need to know a trick to make them last as long as any polish - the top coat sandwich...
Top coats add durability, but they dull the rainbow effect of holos. Instead of skipping it all together, put down a coat or two of the holo, then your top coat, and finish off with more holo. (This works well to add durability under a matte topcoat as well)
I painted my left hand first this way and had to use four coats total of the holo polish. I started thinking, if I'm dulling the bottom layers anyway, why not just start with a normal silver polish first? On my right hand I used two coast of a shimmery silver, the top coat, and then finished with two coats of holo. You could not tell the difference at all, so this is a great way to save money using half of much of the pricey holo! And the wear time was even a little better - the all-holo hand got a few light chips on day 2 & 3 and then I did not have another chip until day 6! (this time on the mixed hand)