My understanding of tetrachromacy is that it's duplicates the red cones, and shifts their sensitivity a very tiny amount - the suspicion is that it doesn't meaningfully change subjective color perception at all, and at best makes tetrachromats very slightly better at distinguishing shades of red that would appear identical to us regular trichromats.

It would be very exciting if some humans had a mutation that let them be sensitive to something further than our standard three!