This lets you use something like this in your $GIT_DIR/config file.
[diff] color = auto
[diff.color] new = blue old = yellow frag = reverse
When diff.color is set to "auto", colored diff is enabled when the standard output is the terminal. Other choices are "always", and "never". Usual boolean true/false can also be used.
The colormap entries can specify colors for the following slots:
plain - lines that appear in both old and new file (context) meta - diff --git header and extended git diff headers frag - @@ -n,m +l,k @@ lines (hunk header) old - lines deleted from old file new - lines added to new file