I have not been able to come across a good definition of color bias, or at least one that I could practically comprehend.
Consequently, what is color bias, why does it or does not occur, and when and when isn't it optically important/significant?
Also, it wouldn't hurt to explain what warm,cool, and neutral signify.
Please go slow as I am only an ex-MSW who never had to take an economics course and obviously never a mechanical engineering course.
http://www.lintuvaruste.fi/hinnasto...culars_GB.shtml
Possibly the best discussion of "color bias" can be found in the short discussions of "color rendition" in the above link. It is an english translation of the Binocular Reviews from the now defunct Finnish Birding Magazine, "Alula." The reviews were written by Kimmo Absetz. (IMHO, these reviews are worth preserving as "Reference Standards" on how binocular reviews should be done.)
With that editorializing out of the way, I think that "color bias" usually is the result of a consensus of opinion among the people who use the specific binoculars in question because there are always some people whose eyesight or interpretation of what they are seeing is different from others. For instance, I own at least 9 Nikons. The general consensus (and it agrees with Kimmo Absetz's assessment) is that Nikon has a color bias toward Red. I don't see this color bias myself. To me, they have the most neutral of color biases. I can easily see the yellow color bias that my old Leitz 7 x 42 Trinovid is notorious for, and there even seems to be a hint of it in my more modern Leica 7 x 42 Trinovid. My little Zeiss 8 x 20 Victory does seem to have a slightly blue, cool, color bias as Absetz notes. I can't comment on Swarovski because I have had very little experience with them.
I wonder if visual phenomena like these are scientifically measurable or if they are subjective interpretations of our brains and our optic nerves, which are connected to our brains after all!
Cordially
Bob
PS: In the link above, click on the review: "Leica 10 x 42 Ultravid Challenges the Elite 10 Power Binoculars" to see a more extensive comparison with other Brands.