I use colour just like in BitTornado. So I copied his descriptions here:
* Green : Everything goes well
* Blue : There are no complete copies among the clients you are connected to. Don't panic, other clients in the torrent you can't see may have the missing data.
* Yellow : You have not received any incoming connections from others. It may only be because no one has tried.it may indicate your system is behind a firewall or proxy server. Please look into routing BitTorrent through your firewall in order to receive the best possible download rate.
* Grey : Waiting to connect to the tracker.
* Red : You have no connections with other clients. Please be patient. If after several minutes the colour is still red, this torrent may be old and abandoned