In iTunes what does [Green] or [Red] mean beside the song?

I don't have any idea where you are referring to. Could be a difference in color settings on monitor.

Playlists in left hand pane have different color icons based on whether list is smart playlist or regular playlist.

How about this
http://support.apple.com/kb/HT2338?viewlocale=en_US

I had no idea what you were talking about since I'm not a SHania fan. So I looked at the iTunes store. From what I can tell the green version has more of a pop sound, and the red version has more of a country flavor.

There's two "Up!" albums - green or red version. So buy the one where the sample sounds best to you.

Katrina is correct. I have both albums. They are mixed differently for a different sound. There was actually a third set available online when the albums originally were released. The online versions were yet another mix. I think one of them had a reggae style.

Red is mixed as Pop and Green is mixed as Country.

http://www.furia.com/page.cgi?type=twas&id=twas0410

And Blue is mixed as "World".

All the same songs.