What are the classifications of color blindness?

Under normal circumstances—assuming no ocular disease—the human eye enables us to perceive a rich spectrum of colors, and there is virtually nothing in the world that cannot be seen with healthy eyes. However, for individuals with color blindness—a common visual disorder—distinguishing many colors proves difficult or impossible in daily life, resulting in a markedly monochromatic perception of the world.

Types of Color Blindness

1. Protanopia (Red Blindness)

Approximately 1% of males worldwide have protanopia. These individuals cannot distinguish red and green hues, while their perception of blue and yellow remains unaffected. Protanopia, also known as “first-type color blindness,” is characterized primarily by an inability to differentiate red. Patients often confuse red with dark green, blue with purple-red, and purple with blue; they may perceive green as yellow, purple as blue, and mix green and blue to appear white.

2. Deuteranopia (Green Blindness)

Deuteranopia is one of the most common forms of color blindness, affecting approximately 4.63% of males—many of whom remain unaware of their condition. Also termed “second-type color blindness,” deuteranopia impairs the ability to distinguish pale green from dark red, purple from blue-green, and purple-red from gray. Green is often perceived as gray or dark black. Clinically, protanopia and deuteranopia are collectively referred to as “red–green color blindness,” the most prevalent form. When people commonly refer to “color blindness,” they typically mean red–green color blindness.

3. Tritanopia (Blue Blindness)

Tritanopia is a rare form of color blindness, occurring with roughly equal frequency in males and females. Individuals with tritanopia confuse blue and yellow but retain normal perception of red and green. It is relatively uncommon. Their visual world resembles a cyan-tinted (“A-Bao”) palette—dominated by bluish backgrounds.

4. Monochromacy (Complete Color Blindness)

True monochromacy does exist, though it is exceedingly rare—occurring in only about 0.00003% of the global population. Monochromacy involves a complete absence of functional cone photoreceptors. In contrast to night blindness (caused by rod dysfunction), monochromats exhibit photophobia and prefer dim lighting—a condition termed “day blindness.”

Color blindness significantly impacts daily life and is hereditary, potentially affecting future generations. Many affected individuals experience diminished self-esteem due to their condition—particularly in professional settings, where color discrimination is essential. Therefore, individuals with color blindness should pay special attention to ocular health and take appropriate measures to protect their vision.