The Martian sky is actually Red- the first few Mars Lander photos were incorrect, as the computer algorithms 'expected' the sky to be blue, and mis-coloured the pictures. I wouldn't bother with clouds- the atmospheric pressure and temperature preclude them. Your best bet, is to have a look at some of the NASA pictures to give you an idea for the colours to use. As to background, have you got VistaPro? Because, at least with the Amiga version, you can output the DEM files, as Turbosilver objects (they are big, however!) I've got the Caldera of Olympus Mons, which I could email you in Imagine format, if you want. There are also a lot of DEMs available of various regions of Mars, mapped by various probes- although the offical ones for VistaPro are expensive. I like the Ice effect on the mountains, it's very effective.

thanks Kevin, Yes Mars is red, but because of the iron oxyde dust in the atmosphere. Say you are in the northen polar cap region, in a day without any dust: crystal clear atmosphere with a white lansdcape surrounding, then, the sky color would not be necesseraly red, I guess it would be rather dark blue or pink , if not black ?

I think the sky should be black with a salmon-pink haze along the horizon to reflect the fact that Mars has such a thin atmosphere.

I don't agree technogeek, if the astronaut is far deep into the polar cap and can only see similar polar cap diffracted light, black-blue, then no red tint shoub be discernable, but if he is standing in the edges and the horizon lie ouside the polar cap (fill with dusty red particles) then yes, the horizon should have a salmon pink tint.