Without too much fuss, Apple released a new version of its OS X operating systems for Mac computers. The great thing about it is, that it's completely free for the existing Mac OS X users.
You can set notifications to find out when your collaborators have modified your spreadsheets, and learn what sheets or cells they've modified. You can also choose how often you'd like to be notified.
Basic tutorial for everyone who want to will learn how to use a dedicated tool for really quick changing of any color you want on a photograph with the help of trusty Photoshop.