My niece Simla took this picture of her dog Chester in Ottawa about a month ago when they had an unusual case of blue snow. Or, maybe they didn't.
When it comes to taking pictures in the snow, the exposure meters of cameras have never been reliable. This is not a problem specific to digital cameras; film cameras had the same issues. The snow is just too bright and it reflects the UV portion of sun light. To get the correct exposure you need to set the camera manually to overexpose.
The blue snow can be corrected in Photoshop. One way of doing it is with the color balance controls: increase yellow to decrease blue and increase red to decrease cyan until the snow becomes white. Usually, it is also necessary to lighten up the picture. Another way, which is faster, is to use the white dropper in the Levels dialog box. Click it on the snow and Chester will be cured of his winter blues instantaneously.