[Culverin]

That sounds like a surveillance drone, nothing out of the ordinary really.
As for the "cloak" mode you're talking about. Just by using lighting to match the surrounding levels, it's quite easy to cloak a small object in the sky. The eye will have a very difficult time locking onto colors, what lights would do is to blend the contrast so it matches the shade of the sky. This matches what you are talking about the light pulsing on and off. It's probably military and they are just testing the light projectors.

The most obvious sign that it's not man made would be ridiculous acceleration and vector changes. To date, there is nothing man made that can do high speed direction changes in the air.