Most color vision problems are inherited (genetic) and are present at birth.
People usually have three types of cone cells in the eye. Each type senses either red, green, or blue light. You see color when your cone cells sense different amounts of these three basic colors. The highest concentration of cone cells are found in the macula, which is the central part of the retina .
Inherited color blindness happens when you don't have one of these types of cone cells or they don't work right. You may not see one of these three basic colors, or you may see a different shade of that color or a different color. This type of color vision problem doesn't change over time.
A color vision problem isn't always inherited. In some cases, a person can have an acquired color vision problem. This can be caused by:
-Aging.
-Eye problems, such as glaucoma, macular degeneration, cataracts, or diabetic retinopathy.
-Injury to the eye.
-Side effects of some medicines.

What are the symptoms?

The symptoms of color vision problems vary:
You may be able to see some colors but not others. For instance, you may not be able to tell the difference between some reds and greens but can see blue and yellow easily.You may see many colors, so you may not know that you see color differently from others.You may only be able to see a few shades of color, while most people can see thousands of colors. In rare cases, some people see only black, white, and gray.
Types of color vision deficiency
Monochromatism: Either no cones available or just one type of them.

Dichromatism: Only two different cone types, the third one is missing completely.

Anomalous trichromatism: All three types but with shifted peaks of sensitivity for one of them. This results in a smaller color spectrum.

Dichromats and anomalous trichromats exist again in three different types according to the missing cone or in the latter case of its malfunctioning.

Tritanopia/Tritanomaly: Missing/malfunctioning S-cone (blue).
Deuteranopia/Deuteranomaly: Missing/malfunctioning M-cone (green).
Protanopia/Protanomaly: Missing/malfunctioning L-cone (red).

How is color blindness diagnosed?

Tests measure how well you recognize different colors.
In one type of test, you look at sets of colored dots and try to find a pattern in them, such as a letter or number. The patterns you see help your doctor know which colors you have trouble with. In another type of test, you arrange colored chips in order according to how similar the colors are. People with color vision problems cannot arrange the colored chips correctly.
Take a Colorblind test below
http://colormax.org/color-blind-test/

Because a color vision problem can have a big impact on a person's life, it is important to detect the problem as early as possible. In children, color vision problems can affect learning abilities and reading development. And color vision problems may limit career choices that require you to tell colors apart. Most experts recommend eye exams for children between ages 3 and 5. Vision screening is recommended for all children at least once before entering school, preferably between the ages of 3 and 4.

How is it treated?

Inherited color vision problems cannot be treated or corrected.
For the most common type of color blindness-red-green color deficiency-no treatment is needed, because you function normally. You may not be aware that you do not see colors the way they are seen by others.

Some acquired color vision problems can be treated, depending on the cause. For example, if a cataract is causing a problem with color vision, surgery to remove the cataract may restore normal color vision.

You can find ways to help make up for a color vision problem, such as:
Wearing colored contact lenses. These may help you see differences between colors. But these lenses don't provide normal color vision and can distort objects.Wearing glasses that block glare. People with severe color vision problems can see differences between colors better when there is less glare and brightness.Learning to look for cues like brightness or location, rather than colors. For example, you can learn the order of the three colored lights on a traffic signal.


Colorblindness Facts

1)Color blindness is not gender blind. In fact it is much more common among men. It affects 1 in every 12 males in this country but less than 1 in every 200 females.

2)Facebook is blue because its founder, Mark
Zuckerberg, suffers from red-green color blindness.

3)In true color blindness facts, people are “color blind” only if they see just black and gray. This is actually very rare. The more common condition is “color vision deficiency,” where greens and reds can look confusing.

4)Color blindness is hereditary, and is passed from mother to son on the 23rd chromosome. However, it can also be caused by eye diseases, aging or retina damage.

5)A fatal railway accident in Sweden in 1875 that killed nine people was believed to be caused by a color blind rail operator who failed to properly read a signal. After the crash, a method to test color vision was developed and applied to railroad workers.

6)It is illegal for color blind people who live in Romania and Turkey to have a driver’s license. The laws in those countries were implemented based on fear that color blind drivers could not read traffic signals.

7In World War II, color blind men were considered to have an advantage since their inability to see green helped them to see through camouflage. Today, the military will not allow people to serve if they are color blind.

8 )Dogs, cats and rabbits see mostly gray. Monkeys have strong color vision while bees and butterflies have superior vision and can see colors humans can’t even see.

9)Not a lot of people, but some, suffer from a rare form of color blindness called unilateral dichromacy which means they have one normal seeing eye, and one color blind eye.

10)People who suffer from red green color blindness have a difficult time determining if their meat is cooked enough. Without being able to see different shades of red, it is hard to tell.

http://www.webmd.com/eye-health/tc/color-blindness-topic-overview
http://www.color-blindness.com/types-of-color-blindness/
http://colormax.org/colorblindness-facts/

50 Other Facts about Color Blindness

#01 99% of all colorblind people are not really color blind but color deficient; the term color blindness is misleading.

#02 Red-green color blindness is a combination of red-blindness (protan defects) and green-blindness (deutan defects).

#03 Color blindness is more prevalent among males than females, because the most common form of color vision deficiency is encoded on the X sex chromosome.

#04 “What color is this?” is the most annoying question you can ask your colorblind friend.

#05 There are three main types of color vision deficiency: protan, deutan, and tritan defects.

#06 Strongly colorblind people might only be able to tell about 20 hues apart from each other, with normal color vision this number raises to more than 100 different hues.

#07 Colored lenses or glasses can improve color discrimination in your problem areas but can not give you back normal color vision.

#08 Ishihara plates are the best known color blindness tests, but they are not the most accurate ones.

#09 About 8% of all men are suffering from color blindness.

#10 Severity of color blindness is usually divided into the following four categories: slightly, moderate, strong, and absolute.

#11 The terms protan, deutan, and tritan are Greek and translate to first, second, and third.

#12 A father can’t pass his red-green color blindness on to his sons.

#13 Dogs are not colorblind.

#14 Color vision deficiency would be a much better term; but it is not as easy to pronounce compared to color blindness.

#15 There are people which are really suffering from complete color blindness, which is called achromatopsia or monochromacy.

#16 Blue-yellow color blindness would be better called blue-green color blindness, as this are more the problem colors.

#17 There exists every nuance of color vision deficiency severity, starting from almost normal color vision up to complete color blindness.

#18 Protanopia, deuteranopia, and tritanopia are types of dichromacy, which means you have only two different color receptors (cones) compared to three with normal color vision.

#19 If a woman is red-green colorblind, all her sons will also be colorblind.

#20 Colorblind people feel handicapped in everyday life, and almost nobody recognizes this.

#21 99% of all colorblind people are suffering from red-green color blindness.

#22 When using color correcting lenses you are wearing two differently colored lenses in your eyes.

#23 Red-green color blindness is a recessive sex linked trait, which causes more men to be colorblind than women.

#24 John Dalton wrote the first known scientific paper regarding color blindness.

#25 Protanomaly, deuteranomaly, and tritanomaly are types of anomalous trichromacy, which means you have three different color receptors (cones) like people with normal color vision but one of them is shifted in its peak.

#26 In certain countries you need normal color vision to get a drivers license.

#27 Deuteranomaly—one form of red-green color blindness—is by far the most common form of color blindness.

#28 More women than men are carriers of color blindness, even though they are not colorblind themselves.

#29 Some people get rejected from a job assignment because of their color vision deficiency.

#30 About 0.5% of all women are suffering from color blindness.

#31 Blue-yellow color blindness is a dominant not sex linked trait, which means both men and women are equally affected.

#32 Red-green color blindness doesn’t mean that you are only mixing up red and green colors, but the whole color spectrum can cause you problems.

#33 The anomaloscope is the most accurate color blindness test known today.

#34 Police officer, firefighter, and airline pilot are the most famous jobs which require normal color vision.

#35 There is no treatment or cure for color blindness.

#36 Pseudoisochromatic plates were introduced by Professor J. Stilling of Strassburg in 1883; the Ishihara plates by Dr. Shinobu Ishihara followed almost half a century later.

#37 Different chromosomes are involved as sources for the different types of color vision deficiency.

#38 Women can also suffer from color vision deficiency.

#39 Monochromacy—also called achromatopsia—means you have only one type of color receptors (cones) in your eyes.

#40 Color blindness is also called Daltonism, after the scientist John Dalton.

#41 The most often used types of color blindness tests are: pseudoisochromatic plates, arrangement test, and the anomaloscope.

#42 Better color vision deficiency terms would be: red-blindness for protanopia, red-weakness for protanomaly, green-blindness for deuteranopia, green-weakness for deuteranomaly, blue-blindness for tritanopia, and blue-weakness for tritanomaly.

#43 John Dalton believed his whole life that the cause of his color blindness is a colored fluid inside his eye balls.

#44 Many colorblind people have problems with matching clothes and buying ripe bananas.

#45 Quite a lot of people with normal color vision can’t pass an Ishihara plates test free of errors.

#46 The International Colour Vision Society is scientifically investigating every aspect of color vision and color vision deficiency.

#47 Confusion lines of the CIE 1931 color space show exactly the colors of confusion for all forms of color blindness.

#48 Only a whole battery of color blindness tests can reveal the true type and severity of your color vision deficiency.

#49 John Dalton was also colorblind himself.

#50 A Colblindor is a colorblind person who learned to enjoy his colorblind life 

http://www.color-blindness.com/50-facts-about-color-blindness/