Coggle is a free and easy mind mapping application that you can sign in to via your Google account. When creating a mind map with their software, Coggle will automatically randomize the color of each branch, although you may change it to whatever color you wish by clicking on the branch you want to change.
When you have completed your mind map, you can download and share it with your friends or co-workers. Not only that, but you may allow the people that you share your mind map with to edit the content too. It also gives you the option to look at what your mind map looked like before you allowed other people to make changes on it.