It's funny that you bring this up, Misha. I had noticed
the coloring in this series and almost mentioned it, but
I had thought it might have been either a natural effect
(such as a prismatic effect on the sunlight due to ice
crystals) or a postprocessing effect. Whichever, it seems
fairly subtle, and since I like color gradients anyway, I
found it to be a pleasent effect.

If it's not a light leak in the camera or bad film, then
the only other explanation I can think of is the prismatic
effect of ice/snow crystals (only a whole bunch of them
spread over the field of view).