Why aren't there many results?

To keep the search interface lightweight and fast, only the first few hundred results are drawn on the screen. There may be more hits in a given area, but they may not be drawn by the interface - this is to improve performance and keep the searches working in real-time.

Why are the flight tracks all different colours?

This is just to help you tell one flight track from another - each one is given a unique colour so that you can tell which one is which if there are several within a small area.