It is better to have green color for text after add to stage area

currently, the git operation text message only be black and red color, when operate in git, after add to stage area, file show green color.

so if in the book can show same color will be better.

@yangwulong1978 Please check out the latest versions of the book when you get a chance:

https://www.raywenderlich.com/books/git-apprentice/v1.1

https://www.raywenderlich.com/books/advanced-git/v1.0

I hope they both help!