Move 256 colors setting into .tmux.conf.

.zshrc

@@ -81,11 +81,9 @@ bindkey "${key[Down]}" history-beginning-search-forward-end
 #
 if [[ "`uname -s`" == "FreeBSD" || "`uname -s`" == "Darwin" ]]; then
     alias "ls=/bin/ls -aFG"
-    alias "tmux=TERM=xterm-256color /usr/local/bin/tmux"
     alias "w=/usr/bin/w -i"
 elif [[ "`uname -s`" = "Linux" ]]; then
     alias "ls=/bin/ls -aF --color=always"
-    alias "tmux=TERM=screen-256color /usr/bin/tmux"
 else
     alias "ls=/bin/ls -aF"
 fi