The subject of the color of fly lines was researched and written about in "The Trout and the Fly" by Brian Clarke and John Goddard. Nick Lyons Books c.1980
An excellent book if you happen to find one.
"What colour of floating flyline is best? All the debate on flyline colour has concentated on the appearances in the air, and on the water in the window.
(The photograph below reveals)the truth.. that it is not the line in the air or window that should be considered, but the line on the water in the mirror.
The white flyline, although it causes a degree of flash in the air, is most of the time less visible to the trout. But it falls like a flash of white lightning across all the water surrounding the trout... across the mirror.
There can be little dought, as a consequence of our experiments and photographs (such as the one below,) that white or light-coloured flylines should not be used when the trout are close to the surface."
The mirror being the area outside of the "cone" or "window" that is the trouts view of the outside world.
This area reflects the world on the underside of the the surface film.
[This message has been edited by dudley (edited 10 December 2005).]
The simpler the outfit, the more skill it takes to manage it, and the more pleasure one gets in his achievements.
--- Horace Kephart