I am going to start by saying this app is absolutely fantastic.
Also as a website, which most designers will be familiar with, this free app is an essential for experimenting with and choosing colour schemes. It selects colours from a photo you can either take or upload, and allows you to save these themes and share them (after signing in with your Adobe ID).
I really find this a useful tool when designing, or simply to play around with for fun! It is interesting to see the colours translating directly from a photograph. I also like how you can search for photographs from Google or Flickr inside the app.