On Earth, the sky is blue and sunsets are red. The reason for this is straightforward: our atmosphere scatters blue light more than it scatters red light, so during the day, that scattered blue light is what we see from all over the sky. When the sun sets and its more direct light is passing through a lot more atmosphere, the blue gets scattered out completely, and we just see purples and reds when we look at it.
On Mars, the effect is reversed, because of (you guessed it) the fact that Mars is a red planet. There's a lot of red dust in the air all the time, which scatters red light, making the sky look a sort of reddish pink during the day. As the sun sets on Mars and the light it emits is more direct, more red gets scattered out, leaving only blue, and creating a bluish sunset. It'll take some getting used to for future residents, but because of the overwhelming amount of red on Mars, we imagine that a blue sunset will be something to look forward to.
Every day, DVICE selects fresh images, videos and more from the wonderful world of technology. See them all by clicking this link.