I'm not usually much into blue nail polish, but when I saw Coastal Surf from Revlon's Colorstay line, I couldn't resist.
It's a bit deeper than a sky blue, has no shimmer, and is nothing if not bright and cheerful. To be quite honest, it reminds me of a Smurf :D
I've only worn it for a day, so I can't comment on its wear time yet, but I have high hopes based on reviews I've read on the range. It was nearly opaque and streak-free in 1 coat and exceeded perfection in 2. I think it'd make the perfect summer pedicure color, too!
What's your favorite blue polish?