When channel mode +n not set, external messages appear with arbitrarily coloured nicks

[miikkas]

When an external message (a message by someone not on that particular channel) is sent to a channel without the mode +n, the nick of that message is coloured with the same colour as the colour of the nick of the previous message on any channel.

I.e., if the nick robot has the colour 2D and says something on some other channel just prior to Spammer1234 sending a message to -n moded channel, Spammer1234's nick will be coloured as 2D.