Change ChannelMsg default to match system default

Change ChannelMsg default to match system default

Change ChannelMsg default to match the system text color palette.

On systems tested, "palette(text)" doesn't refer to pure black, but
instead a very dark gray (60, 60, 60).  Use that as default instead.

This won't affect existing installs as ChannelMsg is stored as
non-default if non-default colors are chosen.