Normally git diff are shown colorless, colored diff are easier to understand since it differentiate addition and removing of code with different colors. You can have it colored with this command:
git diff –color
But if you want it always colored without using –color option, just change the configuration:
git config color.diff true
This make all git diff colored for current repository. If you want to apply it all projects, just change the configuration globally:
git config –global color.diff true