title: Vim: Difference between t_Co=256 and term=xterm-256color in conjunction with TMUX
body: <p>I am testing the various different terminals that I tend to use to SSH into Linux boxes that I have Tmux set up on. </p>
  
  <p>Basically I noticed this behavior, and I am hoping that somebody could offer an explanation of what's going on. Now it may be the case that this is specific behavior that affects the Prompt app. </p>
  
  <p>I am using Vim within Tmux, and on Panic's Prompt app on my iPhone5 I was having the behavior that 256 colors were not enabling when the <code>.vimrc</code> set the colors using the <code>set t_Co=256</code> directive. Here, Vim was correctly displaying the colors when it was not run through Tmux. Also, OS X's Terminal.app correctly rendered the colors (I did not test PuTTY with this on windows unfortunately) with Vim in Tmux. </p>
  
  <p>Then I swapped out <code>set t_Co=256</code> for <code>set term=xterm-256color</code> and now the colors work when using Vim through Tmux. </p>
  
  <p>Note also that I tested both <code>set -g default-terminal "xterm-256color"</code> and <code>set -g default-terminal "screen-256color"</code> settings for Tmux and this change had no effect on behavior. </p>