Sea Siren is a light pink with holographic blue shimmer throughout. It isn't anywhere near as intense as the rest of the line. At first, that did annoy me, but I have learned to appreciate it. It also doesn't have the chunky glitter. It has more of a fine shimmer, so fall out has not been an issue. Because it is more sheer, Sea Siren works best as a shadow topper. It adds the most gorgeous effect to any color underneath it. I do wear it alone if I want an easy look with a slight pop of color.
With flash in outdoor lighting.
Like I said, it is on the sheer side. However, you can layer it for a more opaque finish without much of an issue.
A few people have asked me about the application. I have found that it is best to pat them on with the applicator or your finger. That is the best way to achieve maximum color payoff and it is easier to put the color where you want it. Once this dries, you will want to move quickly because when it sets, it is not going anywhere. I have a swatch on the back of my hand that I keep rubbing and it is not budging at all. The only it will succumb to is the Georgia heat. I get really, really oily when the hot weather hits, so 99% of anything I apply is going to crease or fade. Under normal weather conditions, this shadow will stay put for 8+ hours on me.
Overall, I really like Sea Siren. I do think it is something not everyone will like, though. These are $24 each. They keep going in and out of stock, so if you want one of the new summer shades, you will want to sign up for email notifications. You can get it at Sephora and on Stila's site.