Branch with current implementation: https://github.com/ahf/irssi/tree/256-color-support

Relevant issues tracking this feature:

• Old issue: https://github.com/ahf/irssi/issues/4
• Older issue: 256-Colo(u?)r support shabble/irssi#4
• Oldest issue: 256 colors support irssi-import/bugs.irssi.org#791

Since we're supposed to resubmit issues we care about - this is only issue that made me consider using weechat :D. I don't know the current state of that branch, other than the fact that it's been updated recently.