The above link is always available from the main menu under the Forum option:
The names of people logged into the board and with a Chat channel open (able to see the chat dialog) are listed to the right of the chat window. The colors directly to the left of those names indicate the person's status.
RED=Has not chatted at all
YELLOW=Chatted earlier but dormant for at least five minutes
GREEN=Has posted something in the Chat window within the last five minutes.
For now the CHAT is visible to anyone including GUESTS (people not logged in and non-members), so try not to divulge any state secrets.

If you have any questions or comments on this feature, please do let me know via the site feedback forum.
Cheers,
Ed T.