Emacs: Customize highlight-indentation color

Signed-off-by: Ratheesh S <ratheeshreddy@gmail.com>
Tested-by: Ratheesh S <ratheeshreddy@gmail.com>
Tmux: customization for Tmux

Signed-off-by: Ratheesh S <ratheeshreddy@gmail.com>
Tested-by: Ratheesh S <ratheeshreddy@gmail.com>