Wow.  This is a really interesting to me. Dr Hanlon, a Marine Biologist hypothysizes that an Octopus that has the ability to camoflauge itself by color and texture, does not really MATCH colors to turn invisable. He claims that it revolves arount a fishes perception of invisability that is unique to fish and really has not much to do with color.  This, I think that this applies to fishing in that a fish will sometimes hit a fly that doesnt look like food to us.   Fish perception may not be as straight forward as we assume.