If you are using Ubuntu 14.04, you will have GIMP version 2.8.10 from the official repository. If you want newer version, there is 2.8.16 version from Otto's PPA for Ubuntu 14.04. Thanks to Otto. To install it, follow below instructions.
sudo add-apt-repository ppa:otto-kesselgulasch/gimp sudo apt-get update sudo apt-get install gimpThe PPA page is here.
Addition
To check what version(s) available on your system, type command apt-cache policy gimp. The output will be like this:
gimp: Installed: (none) Candidate: 2.8.16-0trusty2~ppa Version table: 2.8.16-0trusty2~ppa 0 500 http://ppa.launchpad.net/otto-kesselgulasch/gimp/ubuntu/ trusty/main i386 Packages 2.8.10-0ubuntu1 0 500 http://archive.ubuntu.com/ubuntu/ trusty/main i386 PackagesIt means there are two versions of GIMP available. One 2.8.10 from official repository, and another one 2.8.16 from PPA. If you have performed above instructions, then the output will be similar. And if you do sudo apt-get install gimp, the upper version (2.8.16 PPA) above will be chosen to install.