Hawking: A.I. 'worst event in the history of civilization'

As I understand it, the biggest problem with consciousness is that it's mostly (not universally, perhaps, but mostly) defined as a purely subjective phenomena: ie, what we actually experience when we see the color red, as opposed to understanding the machinery that goes into allowing us to see the color (photons, eyes, the wiring of the visual cortex, etc.). If you replicate the machinery of sight, but that machinery exists in a different medium/substrate, will that seeing-thing still experience red in the same way? Perhaps the only way we might could ever know this would be if a human could actually have part of their brains replaced by the same stuff as AIs and were then able to report on whether there was any difference in their conscious experiences before and after.