Terminal 256 colors don't work through tmux

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http://unix.stackexchange.com – I want to set my terminal to 256 colors. I normally use the gnome terminal which is shipped by default in Ubuntu but I also downloaded Terminator and tried Xterm and all them return 8 when I call "tput color". How can I set them to use 256 so I can use vim 256 colorscheme? (HowTos)