the fence color for livestock protection

Switzerland is known for pioneering non-lethal prevention methods towards herd predation, especially when it comes to wolves. Being an European Union partnership country, it leads in active use of livestock-guarding dogs and herding dogs as well as in properly implementing fences passively for livestock protection. Making another step forward, Swiss Agridea - well-known from its herd management workshop organised last year in Graubünden (Calanda Wolfpack territory) - in collaboration with Agrar Fachcenter Weddingstedt Fencemaster (Germany) - developed Flexinet - recommended for the alpine region - in blue and white color exclusively.[1]
– fence net to combine with electric voltage - 90cm high, with rigid vertical struts, mesh size 30cm;
– fence net to combine with electric voltage - 90cm high, without rigid vertical struts, mesh size 30cm;
– blue signal band for being audible fluttering on the fence - 4cm width, 250m long;
– blue-white signal band for being audible fluttering as fladry - 8cm width, 100m long.
Similarly reasoned situation took place in Austria (and Germany) where red color of warning reflectors was changed to blue, to make the wildlife clearly aware of roads which should be avoided (road-kill prevention).

fenced sheep /source: European Wilderness Society/

visible message for livestock closed within a bordered flock
Blue color is not typical for a green grass pasture in natural habitat. Some plants (flowers, blueberry fruits) produce blue color by combination of red pigment (anthocyanin) with other color pigments. Among animals (rare butterflies, some birds) it’s still not the blue color but a combination of pigmented feather barbs or wing scales. Nature didn’t develop the blue color so far. Anyway, the meaning of blue is clear - it’s a warning toward attackers or intruders, and communication that the territory has a resident. Domestic goats same as ungulates - vide sheep or wild deer - evolved retaining horizontally elongated pupils[2] and cyclovergence[3], to be prepared to detect movement of an approaching predator in their surroundings. Currently, the fence in blue is suppose to protect grazing livestock and inform them about no permission to freely go out the separated area.

wolf lucidum wolf of Silesian Beskids, early Summer 2018, by The Association for Nature WOLF

visible warning for migrating/roaming predators
Gray wolf subspecies, as predatory carnivores, are nocturnal. They hunt from dusk till dawn. Their dedicated herbivore prey, living in herds, remaining vigilant, can run fast and camouflage (freezing behavior) if it’s necessary. If stalked/chased the animal runs fast enough, it’s able to outrace its own scent which it left behind. Hunting wolves use tapetum lucidum - an eye layer reflecting light by selected photoreceptor cells, enabling better sight in case of light shortage (during the night for example). Blue color of the fence is above all for searching/tracking predators (scent detecting or following it) information about inaccessibility of potential prey easy to get if not monitored. Fluttering bands play an additional role - deterring them hunting in the dark (along with LGD or instead of them).
visible borderline for pastoral dogs
The domestic dog inherited nocturnal vision basis from a common ancestor with wolves. LGD mostly patrol the guarded area from dusk till dawn (when predators hunt), when nocturnal vision - supported by smell and hearing - is more helpful. Sheepdogs work during the day, doing their job quickly, staying focused on herded animals. They outrun (flanking away from the flock) and flank (moving clockwise/counter-clockwise around the flock). They keep the flock tight during the day, herding livestock from pasture to pasture, then lead them into the enclosure at sunset / out of enclosure after sunrise. Canine field of view is determined by position of the eyes on both sides of the head - visual field of 240°, including 30°-60° binocular overlap (optionally related to dog breed/type/crossbreed). In comparison, human field of view covers - visual field of 180°,[4] including 140° binocular overlap (eyes located in the middle of the head). Fovea centralis is a trait of primates. Wolves and ordinary dogs (including shepherds)[5] use the area centralis supported by visual streak - peripheral, panoramic, high-quality vision.

wolf_dog vision colors

Canine color vision is not monochromatic (complete color blindness) but dichromatic (there are two kinds of cone cells in the eyes, absorbing a different color each one). Impossibility to see green and red colors does not make a living being colour-blind. Humans vision is generally trichromatic (three cone cells types (Red-Green-Blue), full color vision), whereas birds are even tetrachromatic (seeing also near-UV).[6] Likewise sheep, goat or just wild deer, together with the rest of mammals, wolves same as dogs can’t see red and green - their dichromacy seems to be deuteranopia alike (visible wavelength Yellow-Blue). Speaking simply - contrasting fences in blue let herding dogs see bordered area limits specifically and work most securely.
successful herd management implies increased probability of livestock survival
Scientifical evidences point on not colors but their contrast as important for genus Canis (not forgetting that too many tiny outstanding spots means a camouflage). Glary blue fence on originally green pasture or with grey rocks nearby, is extremely apparent.

Proper herd management as the 1st of EU steps to solve agriculture-wildlife conflicts was described some time ago.
In detail about proper fencing as a passive non-lethal predator prevention method you can read in the article about Polish wolf situation.

[1] via European Wilderness Society, Jun 6th, 2018.
[2] Distinctive trait of herbivore prey species with eyes on the sides of their heads. Carnivore predatory species chasing down their prey, have circular pupils (vide canids); ambush-and-pursuit ones have their pupils vertical (vide feline).
[3] Both eyes rotate monocular simultaneously in different/opposite directions, maintaining full panoramic view, when preyed animal is busy grazing.
[4] 200° = 180° + 2x10° for each eye - according to “How Dogs Think. Understanding the Canine Mind” by Stanley Coren.
[5] Mesocephalic dogs have most wolf-like snouts. Dolichocephalic types (vide sight-hounds) perfectly realize what happens at the distance (field vision up to 270°). Brachycephalic ones are better in focus on what happens in front of their eyes.
[6] based on “Animal Cognition: Evolution, Behavior and Cognition”, Clive D.L. Wynne, Monique A.R. Udell, Polish edition by COAPE (2015).
“Inside of the Dog. What Dogs See, Smell and Know”, Alexandra Horowitz, English edition (2010), Polish edition (2011).
Why do animal eyes have pupils of different shapes (2015), at the Department of Physics and Biophysical Sciences Institute (Durham, UK), research by collective work.