irssi has been made for terminals with black background, and once you have one with white background by default (my xterm for better kontrast when coding). on nick highlighting, this is by default yellow, which remains unreadable on a white background (see debian bug). In order to change that, you need to fetch the default theme, and modify it a bit. Or you’ll find a theme which fits for your needs (i didn’t).

$ mkdir .irssi ; cd .irssi
$ cp /usr/share/irssi/themes/default.theme .
$ vim default.theme

  #menick = "%Y$*%n";
  #on white background xterm, yellow is unreadable, change to green
  menick = "%G$*%n";

After that, either chose a different theme, and then the default again…

/set theme foo
/set theme default

or simply quit irssi and start it again.

$ irssi
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