In a Conversation Window type ' /prefs '.
This will open the Preferences Window.
In the Window, click on the 'Customize' tab. Make sure 'Use formatting attributes to color contact names' is checked.
If it is, a program might be interfering with Messenger Plus! and causing in compatibility. Have a look
here and see if you have any of the programs installed.
What version of Windows, WLM & Plus! do you have?