[Primoz]

If you want to correct a color pic you need a busload of additional information - where and when (which time of year, what time of day ...) the photo was taken, otherwise you don't know if the sky is "blue enough" or if the grass is "green enough". You can find many "overcorrected" color photos in various publications. The corrected photo Franek posted may be realistic if it was taken on a sunny afternoon of a cold winter day.