Borrowing a lot from this sage advice, I decided it’s time to figure out 256 color vim on OS X. That meant immediately leaving Terminal.app for dead, since he can’t display more than 8 (16 w/ANSI bold) colors. Here’s the alternative I came up with:

• Installed iTerm.
• In iTerm, hit option+cmd+B for “Profiles”.
  • Under “Keyboard Profiles, Global”, I removed all the mappings and set the “Option Key as” to “+Esc”. This allows me to switch channels in irssi with option+number.
  • Under “Terminal Profiles, Default”, I changed “Type” to “xterm-256color” and checked “Blinking cursor”.
  • Under “Display Profiles”, for “Dark Background” and “Light Background”, I tweaked the “Cursor” colors to be more visible.
• Grabbed this perl script that prints a 256 color test palette to the console. Ran it outside of GNU Screen, and everything looked good.
• Added the following lines to my ~/.screenrc:

#terminfo and termcap for nice 256 color terminal
# allow bold colors - necessary for some reason
attrcolor b ".I"
# tell screen how to set colors. AB = background, AF=foreground
# the first two are for other terminal emulators, just in case.
termcapinfo xterm "Co#256:AB=E[48;5;%dm:AF=E[38;5;%dm"
termcapinfo xterm-color "Co#256:AB=E[48;5;%dm:AF=E[38;5;%dm"
termcapinfo xterm-256color "Co#256:AB=E[48;5;%dm:AF=E[38;5;%dm"
term xterm-256color
# erase background with current bg color
defbce "on"

• Ran the test script inside of GNU Screen, everything looked good.
• Added the following lines to the top of my ~/.vimrc, because apparently “set t_Co=256″ must appear before any syntax and color settings:

set t_Co=256
:colorscheme railscasts

• Started up vim inside GNU Screen, and voila!
• Wrote about it here so I never forget this stuff.