I’ve assumed that the different colors of the flight track and data referred to aircraft leaving or arriving at the airport selected, i.e. KORD would show flights to and from it in blue, and all others green; however I am not sure. Ist there a legend published ?
The legend is clearly printed out along the bottom of the expanded map you get if you click on the smaller map of the airport or flight tracking page.
However, that brings up the point that the ad banner at the top of that map pushes the bottom of the map, and the legend, out of view. A vertical scroll bar would be helpful.
We have this problem fixed in a number of ways internally and you can expect to see the change in the next week or so.