Margin is a unique blush in MAC's permanent collection. It's a powder formula with a frost finish. It's described on MAC's site as being peach with a gold shimmer. Maybe that description is too reminiscent of Nars Orgasm, but I definitely see this as more of a clay color (maybe a burnt peach?) with subtle gold shimmer. Either way, it's one of my favorite go-to blushes.
I'm a self-tanner, and it's hard for me to find products that will work at all the stages of my tanning regime; this blush has kind of become a no-brainer for me. I think this mostly has to do with its red undertones. This gives you just enough warmth to make you look like you've got some sun. When I'm tan, I feel like this really makes my color look more natural. When I'm fair, I usually skip the bronzer and just use this to give me a natural flush that doesn't pull orange. The shimmer in this gives a nice sheen, it's not too much as long as you use a light hand. When I use this, particularly when I have a tan, I apply it a little higher on the cheek bones and slightly inward, where you normally get a little red from the sun, which I've seen GossMakeupArtist do in a few of his videos with reddish tones. Since it does have some shimmer, if you want to try that trick, I do recommend avoiding areas with large pores or finding a similar shade in a matte or cream blush if enhancing pores is a concern.
Overall, I think this is a great product if you're looking for something natural and easy for everyday. I would definitely recommend it if you are a fellow self-tanner or are looking for something that's going to work for you year-round. You can find this a maccosmetics.com or at your local MAC counter for $21.