This nifty tip was provided by Maco on StackEchange’s AskUbuntu forum:

$ sudo nano ~/.bash_aliases

Now, add the following line to the file:

alias grep='grep -n --color=always'

There is an include directive in ~/.bashrc that loads ~/.bash_aliases if it exists

Shell settings go into ~/.bashrc. They impact all terminal users on your server. On the other hand, session settings only impact the user who is logged. These are also called “environment variables” definitions and go into ~/.profile (c.f.