The light from Andromeda Galaxy appears redshifted when viewed from Earth. This means the wavelength of the light is longer and the frequency is lower than it would be if the galaxy were stationary relative to us.

Here's why:

* Doppler Effect: The redshift of Andromeda's light is caused by the Doppler effect. This is the same phenomenon that makes a siren sound higher pitched as it approaches you and lower pitched as it moves away.

* Receding Galaxies: Andromeda is moving away from us due to the expansion of the universe. As it moves away, the waves of light it emits are stretched out, increasing the wavelength and decreasing the frequency.

* Redshift Measurement: Astronomers can measure this redshift by comparing the wavelengths of light emitted by specific elements in Andromeda to the known wavelengths of those elements on Earth. The difference in wavelength tells us how fast Andromeda is receding from us.

It's important to note that Andromeda is actually moving towards our Milky Way galaxy, but this motion is much slower than the expansion of the universe. The overall effect is still a redshift because the expansion of space is dominating the motion.