You can change the colour of the title bar in iTerm with an ansi code! I have different colours for all of my servers: http://i.imgur.com/mdF3XBz.png

This will give you a title bar with RGB values 20, 20, 20:

printf -- $'\033]6;1;bg;red;brightness;20\a\033]6;1;bg;green;brightness;20\a\033]6;1;bg;blue;brightness;20\a'

Documentation: https://iterm2.com/documentation-escape-codes.html