Background color mismatch in vim and tmux

Question

I'm having trouble getting the full range of colors to work in vim when I'm running through tmux. I belive that it's some sort of trouble with TERM variables or 256colors, but I've done everything I have been able to find online to get 256 colors working in vim, tmux, and iTerm, and nothing has fixed it. It's a small problem, but it seriously bugs me.

Here's an example code file in vim just through iTerm:

and here's the same file in vim through tmux and iTerm:

Notice how the background colors seem slightly mismatched, only when code is written there. Why could this be?

I have set t_Co=256 in my vimrc, my iTerm terminal is set to xterm-256color, I have set -g default-terminal xterm-256color in my tmux.conf, and I have:

if [ -e /usr/share/terminfo/x/xterm-256color ]; then
     export TERM='xterm-256color'
else
     export TERM='xterm-color'
fi

in my .profile. This exact issue is replicated on my Ubuntu based machine at work, and I use all of the same configuration files there. This at least isolates the issue as not being OS/iTerm related.

Answer 1

An old question but it ranked high on my Google search without helping me. This is what finally solved this for me

In .tmux.conf:

set -g default-terminal "screen-256color"
set -ga terminal-overrides ",*256col*:Tc"

In .vimrc:

if exists('+termguicolors')
  let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum"
  let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"
  set termguicolors
endif

Answer 2

After adding the line below into .tmux.conf

set -g default-terminal "screen-256color"

You still need to add the line below into .vimrc

set term=screen-256color

Finally, the alias need to be added to .bashrc

alias tmux='tmux -2'

Answer 3

Inside tmux, you need to set TERM=screen-256color. It may be something like here that this only works from inside tmux, but not in tmux.conf. Check that you don't unconditionally overwrite the TERM value, e.g. in your .bashrc, or anything that gets sourced when you open a shell inside tmux.