Volks,
I am digging deep into the noodle for this one but I believe I am remembering
it correctly.   We were studying aerial photography and satellite imaging in a
Remote Sensing class.  The reason the sky(on a clear day) and swimming pools
are blue is because moisture(fog) reflects light primarily in the blue
wavelengths.  This phenomenon is called Rayleigh Scattering.   To counteract
this problem a minus blue(yellow) filter is used in aerial photography to
reduce reflected light and sharpen the image.  I assume it is for the same
reason that they make some sunglasses   and fog lights yellow.
Please correct me if I am wrong.  I was just hoping to  use my Geography
degree in some form other than being in charge of the Road Atlas  when the
band is on the road. :-)
Dan Hall
Alabama