[igiveup]

Ability to perceive your own thoughts. Access to your own debug logs.

I think this is distinct from "ability to perceive green, which doesn't exist". A neural network trained to distinguish green in the output of a spectroscope will perceive green without ever knowing there is something like a "neural network" or "thoughts".

Also, this probably can be detected from the outside via debugging. What cannot be detected may be the thing that distinguishes a hypothetical "philosophical zombie" from a truly conscious human, but I don't think anything like a philosophical zombie exists. Once it is physically identical to the human, it will also be thinking identically.

As a next step, you may observe humans around you and realize that the thoughts you perceive seem to be running inside the head of one of these humans (which you will call "me"). However, I don't think knowing what you look like from the outside is necessary for consciousness.