True Color (24-bit) and italics with alacritty + tmux + vim (neovim)

This should make True Color (24-bit) and italics work in your tmux session and vim/neovim when using Alacritty (and should be compatible with any other terminal emulator, including Kitty).

Testing colors

Running this script should look the same in tmux as without.

curl -s https://gist.github.com/lifepillar/09a44b8cf0f9397465614e622979107f/raw/24-bit-color.sh >24-bit-color.sh
bash 24-bit-color.sh

Configuration files

⚠️ IMPORTANT ⚠️ Don't set $TERM in your shell (zshrc, bashrc, etc.), but your terminal (alacritty).

Alacritty

In ~/.config/alacritty/alacritty.yml:

env:
  TERM: xterm-256color

tmux

In ~/.tmux.conf (or ~/.config/tmux/tmux.conf):

set -g default-terminal "tmux-256color"
set -ag terminal-overrides ",xterm-256color:RGB"

# You can also use the env variable set from the terminal.
# Useful if you share your configuration betweeen systems with a varying value.
#set -ag terminal-overrides ",$TERM:RGB"

vim

In ~/.vimrc:

" You might have to force true color when using regular vim inside tmux as the
" colorscheme can appear to be grayscale with "termguicolors" option enabled.
if !has('gui_running') && &term =~ '^\%(screen\|tmux\)'
  let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum"
  let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"
endif

syntax on
set termguicolors
colorscheme yourfavcolorscheme

neovim

If you use ~/.vimrc for your nvim configuration, use the above vim example because it's fully compatible.

In ~/.config/nvim/init.vim

set termguicolors
colorscheme yourfavcolorscheme

Or ~/.config/nvim/init.lua:

vim.o.termguicolors = true
vim.cmd'colorscheme yourfavcolorscheme'

Not working correctly ?

Check out the comments below for possible solutions.

And if you found another solution I would really appreciate if you left a comment with instructions and the following information:

OS/Distro + version
Vim or Neovim + version
Terminal name + version

Mentions

Shout-out to the nice folks that provided insightful feedback:

@mikeslattery black and white vim colorscheme
@sahibalejandro env variable inside tmux configuration

Exegetech/alacritty-tmux-vim_truecolor.md