Does wavelength affect redshift caused by the metric expansion of space?
Standard cosmological models predicts that the cosmological redshift and the speed of light are wavelength-independent. This result is confirmed observationally e.g. by Ferreras &amp; Trujillo (2016), who used $\sim500\,000$ SDSS galaxy spectra down to a precision of $\Delta z \sim 10^{-6}$ and $\Delta z \sim 10^{-5}$ for galaxies at $z&lt;0.1$ and $z&gt;0.1$, respectively.