tmux config

Active colors

Window/tab bar

In version 3.3 use the answer in comment provided here by @AntK.

set-window-option -g window-status-current-style bg=red
In version 2.9 You should change this options to something like:

Active window title color

setw -g window-status-current-style fg=black,bg=white

https://unix.stackexchange.com/questions/210174/set-the-active-tmux-tab-color

Panel

https://stackoverflow.com/questions/4889724/how-can-you-tell-which-pane-in-tmux-is-focused