“If you see a cloud with a shimmery pastel set of colors in it, that’s because the cloud particles are all nearly identical in size... That’s usually happening just after the clouds have formed and have all grown at the same rate... I always marvel at the colors that show up: reds and greens and blues and purples, it’s really cool to see something shining with lots of color on Mars.”
Source: Mark Lemmon, an atmospheric scientist with the Space Science Institute in Boulder, Colorado, chatting about recent observations made about Martian cloud cover.