Here's why:

* Dust: Mars has a thin atmosphere filled with reddish dust particles. This dust scatters sunlight, giving the Martian sky a pinkish-red hue, especially at sunset and sunrise.

* Wavelengths: The dust particles are more efficient at scattering longer wavelengths of light, such as red and orange, while absorbing shorter wavelengths like blue and green. This is similar to how the Earth's sky appears blue due to Rayleigh scattering.

So, while not exactly pink, the Martian sky often appears a beautiful rosy shade of red!