Sunset on Mars

The reason is that red dust particles in Mars's atmosphere scatter red light just like gas molecules in Earth's atmosphere scatter blue light; there isn't enough atmosphere on Mars for the blue-scattering effect to be significant, so red scattering off of dust particles dominates. That means that when you look near the sun, you see the blue part of the spectrum shining through while the red parts have been scattered off-axis, while in the parts of the sky away from the sun you see the off-axis scattered red.