I was tired of my green shell on my Mac and I really prefer the default shell on Ubuntu. So, I googled a few minutes and find a solution.
First of all, each time you open a new shell, MacOS executes your .bach_profile. (It's quite different on Mac compared to Linux. On Linux, the .bash_profile is executed when you open a new session while .bash_rc is executed each time you launch a shell. On Mac, there's no .bash_rc so we use .bash_profile).
So, let's create/edit your .bash_profile with nano .bash_profile and copy paste the following lines. Restart your shell and enjoy the difference.