Coloring diffs when reading mail in Mutt

This is fairly obvious in theory, but it’s the kind of thing you don’t always think about: when receiving patches via e-mail, it’s possible to have Mutt directly color them as vim or colordiff(1) does. I have this:

  % grep rc_diff ~/.muttrc
  macro   index   \e,sd   ":source ~/.mutt/rc_diff\n" "source ~/.mutt/rc_diff"
  macro   pager   \e,sd   ":source ~/.mutt/rc_diff\n" "source ~/.mutt/rc_diff"

  % cat ~/.mutt/rc_diff
  color body brightblue default   '^\+.*'
  color body brightred default    '^-.*'
  color body brightgreen default  '^(---|\+\+\+) .*'
  color body brightyellow default '^@@ .*'

Update: In case there was some confusion, the rc_diff snippet above is meant to be sourced only when there’s a mail with a patch, otherwise it’ll highlight parts of normail email too. The way to disable again, though, is quitting Mutt...