st + tmux + nvim + True Color + italics

My terminal of choice is st, it is simple and does what it is supposed to do well. I also use tmux and Neovim. Now, I think True Color colorschemes in (Neo)Vim looks awesome; my favourite one is One. Using True Color and italics with st is easy (just add TERM="st-256color" to your shell configuration file, such as .zshrc, though it might even be unnecessary; italics work out of the box), but managing to have them both working in tmux is much trickier. I’ve spent too much time searching the web and trying to make it work, but in the end the solution was quite simple — just add these two lines to your .tmux.conf file:

set -g default-terminal "tmux"
set-option -ga terminal-overrides ",*256col*:Tc"

The first line uses the tmux $TERM, as suggested in the tmux FAQ in order to make italics work. The second line automagically adds True Color support. That’s it!