If Mary is never allowed to actually see the colour of objects in her room, she is being deprived of a physical fact regarding colour vision, and premise 1 does

If Mary is never allowed to actually see the colour of objects in her room, she is being deprived of a physical fact regarding colour vision, and premise 1 doesn't stand. Put another way, how is Mary's later epiphany to be induced in her but by physical means? She must physically experience (photons in eyeballs) colour.