It is useful to set a different color for the shell prompt in different deployment environments like dev/test/production, so that you don't mix up your multiple windows and do something by accident in the wrong window.

• PS1 contains the format of the primary prompt
• \[\e[1;31m\] sets the foreground color to red
• \u will be substituted with the current username
• \h will be substituted with the hostname
• \W will be substituted with the current directory name
• \[\e[0m\] is the end marker of the color setting

To make the color stand out even more for root users, the inverse color can be interesting too:

PS1='\[\e[7;31m\][\u@\h \W]\$\[\e[0m\] '

Other color examples:

#PS1='\[\e[1;32m\][\u@\h \W]\$\[\e[0m\] ' # green
#PS1='\[\e[1;33m\][\u@\h \W]\$\[\e[0m\] ' # yellow
#PS1='\[\e[1;34m\][\u@\h \W]\$\[\e[0m\] ' # blue

You can learn more in man bash, search for "PROMPTING".

Your terminal program must support colors, of course ;-)