Hi buddy you might be colorblind: git diff uses green for added things, not blue. That includes --color-words.

You might've also changed your color theme and forgotten. You can pipe through less (or something else that doesn't understand the control code) and look for ^[[31m is red; ^[[32m is green; ^[[34m would be blue (although ^[[36m is kindof a light blue/cyan) to tell if you've reconfigured your terminal, or you've reconfigured git's default colors, but if you haven't done either you might want to get your color-vision checked!

Oh yes, I found this in my `~/.gitconfig`:

   [color "diff"]
     plain = normal
     meta = bold
     frag = cyan
     old = red
     new = blue