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This depends. If we consider quantum theory, we might be able to deduce that, theoretically, any switch could trigger the bulb - assuming a mechanism had been developed allowing us to harness the power of spinning one particle, by spinning another, seemingly unrelated, particle. With this in mind... the conventional answer seems to be YELLOW :D

yellow the right ans, very nice to mind concentration,keep it up, enjoy my UPVOTE now

Nice thought provoking and educative game. Observational skills are developed.

Tnx@mhangami for resteem