Strange behavior of vim color inside screen with 256 colors

Short Answer

Set TERM to xterm-256color in your .bashrc, and put term screen-256color in your .screenrc.

Long Answer

Here’s why this breaks: gnome-terminal, screen, tmux, bash, putty and vim have all been written to intelligently handle 256 colors, but you need to set things up correctly at the earliest possible point. Using termcapinfo in your .screenrc is actually a duct tape solution!

If your TERM is set correctly, it will signal to bash that you’re in 256-color mode, which means it will play nice with screen being in 256-color mode as well.

So, in your .bashrc, export TERM=xterm-256color. [1]

In your .screenrc, use screen-256color for TERM instead of xterm-256color, and delete the rest of the cruft!

In your PuTTy configuration, use putty-256color.

You can download the termcap entry files and put them in ~/.terminfo/s and ~/.terminfo/p, if your box doesn’t have them by default.

Footnotes

[1] Setting TERM to xterm-256color in your .bashrc can be a little presumptuous, especially if you use the same .bashrc on multiple machines. I have found the following snippet to be fairly effective:

case "$TERM" in
*-256color)
    alias ssh="TERM=${TERM%-256color} ssh"
    ;;
*)
    POTENTIAL_TERM=${TERM}-256color
    POTENTIAL_TERMINFO=${TERM:0:1}/$POTENTIAL_TERM

    # better to check $(toe -a | awk '{print $1}') maybe?
    BOX_TERMINFO_DIR=/usr/share/terminfo
    [[ -f $BOX_TERMINFO_DIR/$POTENTIAL_TERMINFO ]] && \
        export TERM=$POTENTIAL_TERM

    HOME_TERMINFO_DIR=$HOME/.terminfo
    [[ -f $HOME_TERMINFO_DIR/$POTENTIAL_TERMINFO ]] && \
        export TERM=$POTENTIAL_TERM
    ;;
esac

The alias of ssh is a defensive measure to prevent us from trying to open a 256-color terminal on a remote machine that doesn’t necessarily support it. The main block is the other half of the equation; it checks to see if the corresponding terminfo entry exists, and sets it if it does.