biophysics - Is human vision sensitive to frequency or wavelength?

In a vacuum, there is a one-to-one correspondence between light frequency ($\nu$) and wavelength ($\lambda$), ie. $\lambda=c/\nu$. But in a refractive medium, $\lambda=v/\nu$, so while the frequency may remain constant, the wavelength may not.

I've seen that in biology, wavelength is mostly used. But, I recall reading that human vision is sensitive to frequency. So, is human vision sensitive to wavelength or frequency?