"A dark eye blends with the surrounding hair colour, creating a harmonious and trusting, calm, steady look. A light eye, by contrast, stands out sharply. In dogs, that contrast is read by the human brain as high tension, threatening and maybe a a dog that will display aggression.
Breed standards absorbed this instinctive perception. Dark eyes signal calm, steadiness and reliability, qualities we want to see reflected in a working dog’s face. A lighter eye can give an impression of unease and overt sharpness, the feeling the dog might deliver an unprovoked bite, even when the dog’s character is absolutely sound and good natured. This is why some judges, often unconsciously, weight eye colour more heavily than construction or gait. To them the disruption of harmony is too great.
This helps explain why reactions vary. Some judges at a subconscious level are more sensitive to disharmony in expression and therefore penalise light eyes heavily, while others weigh it as a secondary feature behind construction and movement."
