The crosswalk signal has changed from a white figure to a flashing orange hand
you are approaching head on.
look both ways carefully.
it tells you the boat is approaching you head on
You are approaching the stern of another vessel
a boat is approaching you head-on
A vessel displaying a visible white light signifies that it is a power-driven vessel. Observing this light helps determine the vessel's status and potential course of action to avoid a collision.
You must STOP, and wait until GREEN then GO.
Cleared to cross
It's a runway guard light. It's to advise aeroplanes that they are approaching the runway and should stop until advised to the contrary.
Sail boat is coming at you
When the traffic light comes into view and it's green, it was likely green for a long time, unless you also observe cars just starting to get going. If you see the traffic light is green in the distance we call this green light "stale", meaning it could turn yellow any second. A traffic light that just turned green, we call this green light "fresh", meaning it just turned green and it won't be turning yellow for a little while. Of course these times between from when it turns green then back to yellow and red again varies on the intersection. To answer the question when you're approaching a green traffic light you should prepare to stop as that green light is "stale". You don't necessarily have to slow down just get ready to hit the brake.
If you are operating a powerboat at night your green side light must be visible to boats approaching over an arc of the horizon 112.5 degrees and so fixed as to show the the light from right ahead to 22.5 degrees abaft of the beam on its respective side.