I thought I was buying my last Formula X polish a month or so when I bought Ignite - but then I looked later and they had some more polishes on the website, and well, I just can't resist a $5 polish (especially if it's marked down from $12.50 or whatever it was) so:
Prism is super-shimmery. This blogger calls it a neon but I don't see it as quite that bright. It's a pretty color, though.
Marine, I really like more. It reminds me of Zoya Liberty although it's by no means a dupe. Liberty is more of a bright blue I think - I'm going to have to check. But Marine has some texture to it and the color seems pretty similar.
(Added, months later: it is now June, and to my surprise, Sephora put another big set of Formula X's on the website a couple of weeks ago - for I think $2? but I didn't see that they were there early enough and by the time I looked everything that interested me was gone. So I do not have to take back what I said before, these are still my last Formula X's, at least so far!)