I remember Stephen Pinker in How the Mind Works briefly addressing this problem that has haunted me for decades, and dismissing it.
I've been scanning the pages, looking for a reference, and found this (p 146):
Might your experience of red be the same as my experience of green? Sure, you might label grass as "green" and tomatoes as "red," just as I do, but perhaps you actually see the grass as having the color that I would describe, if I were in you shoes, as red.
Pinker's answer to this and similar quandaries of subjective experience is "Beats the heck out of me!"
At least for now, we have no scientific purchase on the special extra ingredient that gives rise to sentience. As far as scientific explanation goes, it might as well not exist. It's not just that claims about sentience are perversely untestable; it's that testing them would make no difference to anything anyway.
And so he relegates this topic, and others, to late-night dorm-room bull sessions and similar forums.
There you have it. Do we really see the same colours? Who cares!