Colorful Tmux panes

Thanks to this commit, we are able to style an individual pane in Tmux. You will have to build Tmux from source to do that. Try:

$ tmux select-pane -P 'bg=green'

And you will get something like:

We could use that to highlight an important pane. I have set key-bindings M-1 to M-4 to different background colours, and M-0 to the default colour:

bind-key -n 'M-0' select-pane -P 'bg=default'
bind-key -n 'M-1' select-pane -P 'bg=black'
bind-key -n 'M-2' select-pane -P 'bg=green'
bind-key -n 'M-3' select-pane -P 'bg=blue'
bind-key -n 'M-4' select-pane -P 'bg=red'

Thanks @thomas_adam for mentioning this feature in the #tmux channel.