Someone Explain This, Please

Why is it that photos like this one of Mars, taken by the Hubble Space Telescope, clearly show the Martian sky is blue. Look at the limb of the planet. But when NASA releases their photos from the surface of the planet, the sky is red, or even salmon? I really do wish they would stop the "color correcting" and just show us a dusty, blue sky.

UPDATE: Friday on Slashdot, there was this thread on the topic. Mostly silly, but some good explanations about color filters, etc. There was a link to a "correct" version of the Martian panorama picture from the Spirit.