Achromatopsia can be inherited but can also result from progressive eye diseases such as retinitis pigmentosa. This is called monochromacy or achromatopsia.

In very rare cases, a person can be completely color blind, meaning they see only the intensity of light, but not its color. Blue-yellow color blindness is usually caused by age-related eye conditions such as glaucoma, or exposure to certain chemicals or medical treatments.

Other types of color blindness exist also, such as tritan-type CVD, also called blue-yellow color blindness, which is associated with the inability to see shades of blue, and confusions between blue and green colors. Red-green color blindness is usually inherited via X-linked recessive genes. These confusions are typical of what is called “ red-green color blindness,” which includes protan-type CVD (protanomaly and protanopia) and deutan-type CVD (deuteranomaly and deuteranopia). When a person is color blind, also called color vision deficiency (CVD), they usually have difficulty distinguishing between certain colors such as yellow and orange, green and brown, pink and gray, or blue and purple. What is color blindness? Color blindness is a reduced ability to distinguish between colors when compared to the standard for normal human color vision. When the ability to see color is deficient, as in the case of color blindness, there is a dulling of what is seen or one might say there is a dulling effect in how we see. It is deeply ingrained in our basic perception of the world. We also use color to interpret information such as signs and lights. It entices us to eat certain foods and buy certain jewelry, and sometimes it literally defines these things. Color is emotional, experiential, and tactical. Colour vision deficiency (colour blindness).Molecular genetics of selected ocular disorders. The assessment of visual function and functional vision. What is color blindness? American Academy of Ophthalmology.Exposure to some chemicals in the workplace, such as carbon disulfide and fertilizers, may cause loss of color vision. Your ability to see colors deteriorates slowly as you age. Some medications can alter color vision, such as some drugs that treat certain autoimmune diseases, heart problems, high blood pressure, erectile dysfunction, infections, nervous disorders and psychological problems. One eye may be more affected than the other, and the color deficit may get better if the underlying disease can be treated. Some conditions that can cause color deficits are sickle cell anemia, diabetes, macular degeneration, Alzheimer's disease, multiple sclerosis, glaucoma, Parkinson's disease, chronic alcoholism and leukemia. Inherited color deficiencies usually affect both eyes, and the severity doesn't change over your lifetime. You can inherit a mild, moderate or severe degree of the disorder. It is rare to have no color vision at all. The most common color deficiency is red-green, with blue-yellow deficiency being much less common. Inherited color deficiencies are much more common in males than in females. But if your cones lack one or more wavelength-sensitive chemicals, you will be unable to distinguish the colors red, green or blue.

If your eyes are normal, you perceive color. Chemicals in the cones trigger a reaction and send the wavelength information through your optic nerve to your brain. The cones are sensitive to short (blue), medium (green) or long (red) wavelengths of light. Light, which contains all color wavelengths, enters your eye through the cornea and passes through the lens and transparent, jellylike tissue in your eye (vitreous humor) to wavelength-sensitive cells (cones) at the back of your eye in the macular area of the retina. Seeing colors across the light spectrum is a complex process that begins with your eyes' ability to respond to different wavelengths of light. There's no cure for inherited color deficiencies, but if illness or eye disease is the cause, treatment may improve color vision. It's important that children get comprehensive eye exams, including color vision testing, before starting school. If you suspect you have problems distinguishing certain colors or your color vision changes, see an eye doctor for testing. Often, a person who is red-green or blue-yellow deficient isn't completely insensitive to both colors. The most common color deficiency is an inability to see some shades of red and green. People affected by color blindness may not be able to distinguish: Some people figure out that they or their child has the condition when it causes confusion - such as when there are problems differentiating the colors in a traffic light or interpreting color-coded learning materials. You may have a color vision deficiency and not know it.

Kid color blind test