It looks just like a standard glitter in the bottle.
So while I didn't get what I expected, I can't complain. This polish is just gorgeous. It's not like a regular glitter polish at all: it's not flat, multicoloured glitter or anything. There appears to be a whole bunch of different kinds of red glitter in it, which makes it look 3D. So it may not have the rainbow holo effect, but it's certainly not a straight, boring glitter. The base is also red, so I had full opacity with two coats. The great thing about it is it applies like a holo in that it's super smooth and dries very fast.
Indoors. See how it's all red: no rainbow?
Interestingly, if you take a look at the More Nail Polish blog here, there's a comparison between this one and number 518, which is a true red holo. Even the photos of 621 there kind of look different to mine: I wasn't able to get any kind of rainbowness to show up, even sparsely. I still love the idea of a red holo, so may cave in and get number 518, too.
In the sun. See how it looks 3D? Love!
I can't be disappointed with this polish. True, it's not exactly what I wanted, but I got something unique (to me, anyway) and unlike any other polish in my collection. All it means is that my yearning for a red holo is yet to be realised.