What is "color blindness"

Blindness \Blind"ness\, n. State or condition of being blind, literally or figuratively.
--Darwin.

Color blindness, inability to distinguish certain color. See Daltonism.

Color \Col"or\ (k[u^]l"[~e]r), n. [Written also colour.] [OF. color, colur, colour, F. couleur, L. color; prob. akin to celare to conceal (the color taken as that which covers). See Helmet.]

1. A property depending on the relations of light to the eye, by which individual and specific differences in the hues and tints of objects are apprehended in vision; as, gay colors; sad colors, etc.

   Note: The sensation of color depends upon a peculiar function of the retina or optic nerve, in consequence of which rays of light produce different effects according to the length of their waves or undulations, waves of a certain length producing the sensation of red, shorter waves green, and those still shorter blue, etc. White, or ordinary, light consists of waves of various lengths so blended as to produce no effect of color, and the color of objects depends upon their power to absorb or reflect a greater or less proportion of the rays which fall upon them.

2. Any hue distinguished from white or black.

3. The hue or color characteristic of good health and spirits; ruddy complexion.

   Give color to my pale cheek.
   --Shak.

4. That which is used to give color; a paint; a pigment; as, oil colors or water colors.

5. That which covers or hides the real character of anything; semblance; excuse; disguise; appearance.

   They had let down the boat into the sea, under color as though they would have cast anchors out of the foreship.
   --Acts xxvii. 30.

   That he should die is worthy policy; But yet we want a color for his death.
   --Shak.

6. Shade or variety of character; kind; species.

   Boys and women are for the most part cattle of this color.
   --Shak.

7. A distinguishing badge, as a flag or similar symbol (usually in the plural); as, the colors or color of a ship or regiment; the colors of a race horse (that is, of the cap and jacket worn by the jockey).

   In the United States each regiment of infantry and artillery has two colors, one national and one regimental.
   --Farrow.

8. (Law) An apparent right; as where the defendant in trespass gave to the plaintiff an appearance of title, by stating his title specially, thus removing the cause from the jury to the court.
   --Blackstone.

   Note: Color is express when it is averred in the pleading, and implied when it is implied in the pleading.

   Body color. See under Body.

   Color blindness, total or partial inability to distinguish or recognize colors. See Daltonism.

   Complementary color, one of two colors so related to each other that when blended together they produce white light; -- so called because each color makes up to the other what it lacks to make it white. Artificial or pigment colors, when mixed, produce effects differing from those of the primary colors, in consequence of partial absorption.

   Of color (as persons, races, etc.), not of the white race; -- commonly meaning, esp. in the United States, of negro blood, pure or mixed.

   Primary colors, those developed from the solar beam by the prism, viz., red, orange, yellow, green, blue, indigo, and violet, which are reduced by some authors to three, -- red, green, and violet-blue. These three are sometimes called fundamental colors.

   Subjective color or Accidental color, a false or spurious color seen in some instances, owing to the persistence of the luminous impression upon the retina, and a gradual change of its character, as where a wheel perfectly white, and with a circumference regularly subdivided, is made to revolve rapidly over a dark object, the teeth of the wheel appear to the eye of different shades of color varying with the rapidity of rotation. See Accidental colors, under Accidental.

1844, replacing Daltonism (after English chemist John Dalton, 1766-1844, who published a description of it in 1794); in figurative use, with reference to race or ethnicity, attested from 1866, American English. Related: color blind (adj.).

n. 1 (context pathology English) Any of several medical conditions in which the physical ability to see colors is impaired, especially achromatopsia, Daltonism. 2 (context figuratively English) indifference to a person's skin color or race.

n. genetic inability to distinguish differences in hue [syn: colour blindness, color vision deficiency, colour vision deficiency]

Color blindness, also known as color vision deficiency, is the decreased ability to see color or differences in color. Color blindness can make some educational activities difficult. Buying fruit, picking clothing, and reading traffic lights can also be more challenging. Problems, however, are generally minor and most people adapt. People with total color blindness may also have decreased visual acuity.

The most common cause of color blindness is due to a fault in the development of one or more of the three sets of color sensing cones in the eye. Males are more likely to be color blind than females as the genes responsible for the most common forms of color blindness are on the X chromosome. As females have two X chromosomes, a defect in one is typically compensated for by the other, while males only have one X chromosome. Color blindness can also result from physical or chemical damage to the eye, optic nerve, or parts of the brain. Diagnosis is typically with the Ishihara color test; however a number of other testing methods also exist.

There is no cure for color blindness. Diagnosis may allow a person's teacher to change their method of teaching to accommodate the decreased ability to recognize color. Special lenses may help people with red-green color blindness when under bright conditions. There are also mobile apps that can help people identify colors.

Red-green color blindness is the most common form, followed by blue-yellow color blindness and total color blindness. Red-green color blindness affects up to 8% of males and 0.5% of females of Northern European descent. The ability to see color also decreases in old age. Being color blind may make people ineligible for certain jobs in certain countries. This may include pilot, train driver, and armed forces. The effect of color blindness on artistic ability; however, is controversial. The ability to draw appears to be unchanged and a number of famous artists are believed to have been color blind.