Support for colour (yes, with a u) in the iOS SDK has always been quite basic but this library by Vicc Alexander changes that. Just a quick look at the documentation tells you this is a comprehensive library. With support for everything from a better default palette, hex support, grabbing colours from images and commonly needed utilities like picking contrasting colours, it's definitely worth a look.
This looks interesting. It takes Core Bluetooth and adds a higher level abstraction on top of it, all written in Swift. If you're not looking for low level control of Bluetooth communication this library by Rasmus Taulborg Hummelmose looks like a good place to get started with something simpler.
Blurable is a new library by Simon Gladman and caught my eye for two reasons. First of all, who doesn't love a blur library. 😄 Secondly the implementation is interesting as it's been created as a protocol extension in Swift. Matthijs Hollemans also published a great article on protocol extensions this week which is worth a read.