Ubuntu – How to change the color of particular file

I had same issue and went through various files in home folder. And found following instruction in ~/.profile

    # ~/.profile: executed by the command interpreter for login shells.
    # This file is not read by bash(1), if ~/.bash_profile or ~/.bash_login
    # exists.
    # see /usr/share/doc/bash/examples/startup-files for examples.
    # the files are located in the bash-doc package.

I added necessary changes in .bash_login instead So it seems that you may have to remove .bash_profile if its present or make these changes to .bash_login or point to to source as .bashrc in .bash_login

    source ~/.bashrc

If you really need to get the number of terminal you have open, go for counting the files owned by you under /dev/pts (although this might include ones opened by background processes, not by graphical terminal emulators). Alternatively, count the number of child processes of your terminal emulator(s), as shown by Jacob in the first line of his response.

Avoid relying on who's output, and looking for gnome-pty-helper processes, since these don't work in newer gnome-terminal versions.

Note that nowadays pretty much all graphical terminal emulators (including putty) and multiplexers (screen, tmux) support 256 colors. You can get really nice colored prompts if you use this palette.

My recommendation for a very simple solution is to base the color on the current tty line's number. E.g. process the output of the tty command to take the number only and derive the color from that. A certain tty line number is only given to one terminal at a time, you'd have to close that terminal first before the same line number is reissued by the kernel. This, combined with 256 colors, automatically guarantees that you won't see the same color twice at a given time (and even with 16 colors it'd give a quite even distribution). No need for maintaining a global counter, and no need for counting terminals or processes.