[Gerald C Koch]

At higher altitudes there is more light from the shorter wave part of the spectrum. This means more blue, violet and ultra-violet. In other words the color temperature of the light is higher than at sealevel. Average color temperature at sealevel is ~5600K while at higher altitudes it can be 10,000K or higher.

Try using a Wratten 1A (skylight) filter first and if this does not provide enough correction then try a Wratten 2A filter. There is a similar problem on overcast days. On gray, dreary days I use a Color Correcting filter such as a CC 05R (red) or CC 05M (magenta) filter to warm things up a bit. You will have to do some experimenting as to which filter provides the best results for you. Here is a list of the Wratten filters. http://en.wikipedia.org/wiki/Wratten_number

Each color film has its own spectral response. Perhaps a different film might work better. Some emphasize cooler tones while others warmer ones.

The color temperature of daylight is effected by several factors such a the position of the sun. Thus the color temperature is highest just before sunrise. I would suggest that anyone who is a serious color photographer read up on this subject.