Why Do Doctors Wear Green or Blue Uniforms? The Scientific Reason

Why do the white coats seen roaming hospital corridors give way to green and blue the moment you step into the operating room? This isn't an aesthetic choice — it's an optical engineering problem solved a century ago. Here's the science, history, and today's reflections in the Turkish healthcare system behind operating room colours.

The End of the White Era in Medicine and the Glare Problem

Until the early 20th century, the absolute clothing of physicians and surgeons was the white coat. White was the greatest physical proof of sterility and medical hygiene at a time when germ theory was starting to gain acceptance — the smallest stain on it could be spotted instantly.

However, the electric, high-focus bright lighting systems that began to be used in operating rooms in the early 1900s turned white clothing into a serious operational obstacle. When strong light hit white fabric, it caused a severe glare that blinded surgeons. Being exposed to this glare during long, delicate operations brought eye strain, migraines, difficulty focusing, and an increased risk of surgical error.

Dr. Harry Sherman's 1914 Reform: Spinach-Green Operating Rooms

The first scientific revolution to eliminate this negative effect of white was carried out in 1914 by American surgeon Dr. Harry Mitchell Sherman, who worked at St. Luke's Hospital in San Francisco. Based on his studies of human colour perception, Sherman argued that green should be used instead of white to prevent light glare in operating rooms and increase a surgeon's sensitivity to tissue.

Sherman designed an operating room at St. Luke's Hospital in which the walls, floor coverings, operating table linens, sheets, and surgical team's clothing were all set to what he called "spinach green." In his scientific papers, he explained that green was the tone that tired the human eye the least, was the most familiar in nature, and passively calmed the nervous system. The practice was quickly adopted by modern hospitals across North America and Europe.

The Anatomy of the Optical Illusion: The Afterimage Effect

The core physiological mechanism behind the preference for green and blue is an optical illusion in the retina called the "afterimage" effect. The human retina has three groups of cone cells: those sensitive to red (L-cone), green (M-cone), and blue (S-cone).

When a surgeon focuses on red tissue, internal organs, and blood for hours, the red-sensitive (L-cone) cells in the retina are continuously stimulated and, after a while, become fatigued and desensitized to the red wavelength. When the surgeon turns their eyes to a white surface, the fatigued red cones can't fully perceive this colour, while the unfatigued green-blue cones continue to be stimulated normally. As a result of this unbalanced signal, the brain forms green-blue ghost shadows (afterimages) on the white background.

These ghost shadows can obscure the surgeon's field of view and cause a loss of focus during millimetre-precision incisions. However, if the uniforms and linens in the operating room are already green or blue, the ghost shadows that form are directly absorbed (neutralized) by this background. This way, the surgeon's eyes rest and their sensitivity to red stays fresh.

The Colour Spectrum and Red's Contrast Balance

Colours located directly opposite each other on the colour wheel (contrasting colours) increase each other's distinguishability when placed side by side. The exact opposite of red on the light spectrum is the green and blue wavelengths.

Wearing green or blue scrubs in the operating room allows the surgeon to perceive even the smallest tonal differences in red within the surgical field (for example, the difference between bright red arterial blood and dark red venous blood) with sharp contrast. This high contrast helps distinguish capillaries from surrounding tissue at the millimetre level, directly increasing the success rate of the operation.

The Psychological and Physiological Effects of Hospital Colours

The direct physiological effects of colours on the autonomic nervous system have been proven by clinical studies. Over the course of evolution, green and blue have become associated in the human brain with concepts of safety, water sources, nature, and calm:

• Physiological calming: Lowers the patient's sympathetic nervous system activity, reducing heart rate, slowing blood flow, and suppressing cortisol secretion — a patient about to undergo an operation experiences a calmer process.
• Focus and mental stamina: Creates a calming and concentration-boosting effect in operating room staff, delaying mental exhaustion during long operations.

The Modern Turkish Healthcare System and the Specialty Colour Standard

The Corporate Identity Guide implemented by the Turkish Ministry of Health in 2025-2026 has extended this colour psychology and functional perception standard to all hospital departments. According to the guide, staff groups are defined by the following Pantone codes:

You can find the full detail of this guide's staff groups and colour codes in our Ministry of Health Uniform Colours guide.

Frequently Asked Questions

Why aren't surgical uniforms black or white? White uniforms cause glare and reflection under bright operating room lights. Black uniforms, on the other hand, obscure the colour of blood, hindering the tracking of leaks and bleeding. This is why green and blue offer the ideal contrast.

How does the "afterimage" effect create a danger during surgery? When a surgeon who has been looking at red blood continuously turns their eyes to a white surface, they see green-coloured ghost shadows due to the fatigue of the retinal cells. This can blur their field of vision and lead to millimetre-level errors.

What is the physiological effect of the colour green on patients? The colour green has a calming effect on the autonomic nervous system, slowing heart rate, lowering blood pressure, and reducing anxiety, easing the patient's pre-operative stress.

Qule Uniform's Optical and Hygiene Standards

Qule Uniform manufactures by analyzing the requirements of medical colour theory and eye physiology. The QuleLITE™ and Atlas series, developed for surgical operations and operating room use, are produced in pine green, sax blue, and lilac tones with a matte weave technology that doesn't reflect under surgical spotlights.

Green and blue scrubs models with Advanced Flex™ technology don't just offer optical comfort; thanks to their silver-ion antimicrobial coating, they also minimize the risk of cross-contamination in the operating room. Thanks to colour-fastness technology, they don't lose their colour or texture even through 60°C and 90°C sterilization washes.

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