Set the active tmux tab color

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

There's an argument with a decent explanation here: https://github.com/tmux/tmux/issues/1689

And the FAQ: https://github.com/tmux/tmux/wiki/FAQ#how-do-i-translate--fg--bg-and--attr-options-into--style-options

You haven't set window active background color, you only set active panel border, try:

set-window-option -g window-status-current-bg red