The picture was of a pink gammarus imitation, which of course is a massive contradiction in itself. I've never tried, but I'm fairly certain that if you cook a gammarus, it turns light pink like shrimp, lobsters, crabs etc. But - a trout has never seen a cooked gammarus.
None the less, pink flies work well in winter cold water, and it could be fun fishing two pink flies on the leader for a few days. One the gammarus imitation and one just a hook with some brushed out pink dubbing of the same type used for the imitation. To be honest, I'm certain they'd score equally well. And yet - I'd still fish the imitation. It just makes me feel better and believe a little more in the fly.
There's a Danish sea trout fly called Kobberbassen (Copper Bully). It's a small(ish) hook with copper flash dubbing brushed out, and that's it. And the reality is that Kobberbassen is a great fly that fishes really well year round. I'm 100% certain it's not taken for a sandeel, but sea trout definitely find it worth checking out if it's edible.
I sometimes fish a pink sandeel imitation as well, and that too works well. I know that many of the fish we catch in the salt (and elsewhere) probably would have taken many other flies than the one that happened to be on the leader, on that particular cast, at that particular time etc., but I've also been in plently of situation where, as far as I could deduce, the right fly made the difference. That's why it's worth having well assorted boxes after all.
The fly was tied as part of my contribution to T.Z.'s flytying iBook (available in Apple iBooks - https://itunes.apple.com/us/book/id1333532292), and if you're interested in a step-by-step, you can find it in his book. I want to thank Thomas for the opportunity to contribute.
I tied a different version for the Ahrex YouTube channel, which I also like fishing. And by the way - check out the brand new freshwater range of hooks by Ahrex. I've had some samples for a while, and they are really fine hooks.
Have a great weekend!