You will see it the same, regardless of the refraction index of your medium. The reason is as simple as that, when the light hits your retina, it will be travelling through the interior of your eye, so the only refractive index that matters is that of the eye.
What is what we actually detect, wavelength of frequency? Frequency is the one related to energy, so my feeling is that that should be the one influencing chemical reactions, that is, at the end, the way cones can detect light.
Indeed, the vitreous humour (the interior filling of the eyeballs) looses water with age, to the point of getting deatached from the retina, something very common among old people (Wikipedia says 75% of > 65). The main consequences are visual artifacts, but no one has claimed colours suddenly look different.
Physics books quote wavelengths because those are usually what one measures in the lab in the optical range. Plus, the numerical values are (and this is subjective) more convenient.