When One get "HLed" on a channel which is not the current channel, the channel name in the list become blue.
But, when a "Channel Msg Hilight" is throwed by a Python script (I didn't test with other scripting languages), the message is hilighted, but the channel name don't become blue, even if I am not on it.
I compiled XChat myself on Ubuntu Lucid. The version is the 2.8.8, from SVN repository (revision 1444). Here are the compiling parameters : ./configure --enable-ipv6 --enable-xft --enable-python --disable-perl --disable-tcl