Make a vision test including red letters among black ones. Ask the person under test to read the red letters. A colorblind person usually can't easily spot red letters mixed in into black. Let the person name colors.
There are 2 main tests for colour vision deficiency: the Ishihara test, where you'll be asked to read images made up of coloured dots. colour arrangement tests, where you'll be asked to put coloured objects in order of what shade they are.
Almost half of all color blind people are unaware of their condition, while 60% of sufferers experience many problems in everyday life. Most color blind people are able to see things as clearly as other people but they are unable to fully distinguish red, green or blue light.
#3: Which colors do you see then? All colors, many colors, less colors. Nobody suffering from color blindness can answer you this questions correctly. Some may see more, some less but none can tell you which colors, because a colorblind person doesn't know how you see the world.
Red-green color blindness
The most common type of color blindness makes it hard to tell the difference between red and green.
The picture below shows that for all of the types of color blindness there is a pair of colors that can be distinguished – red and blue – these are color blind safe colors. As for the green, it is the number one among the colors to avoid for the color blind.
Looking up at the sky could be just the same color as looking down at the ground of grass. Yellow and red also will appear to be pink. Due to a lack of blue cone cells, blue once again appears green. The difference from tritanomaly is that green and yellow seems grey or shades of purple.
Deuteranomaly causes green colors to look red. Protanomaly causes red colors to look green. Protanopia is when you cannot see red light. People who have protanopia color blindness are red-blind and see more green than red.
Tritanomaly—faulty blue cone. This condition is the least common form of color vision deficiency. Individuals with tritanomaly see the world in shades of pink (standing in for orange, yellow, and red) and turquoise (standing in for blue, green, and violet).
Achromatopsia is also known as “complete color blindness” and is the only type that fully lives up to the term “color blind”. It is extremely rare, however, those who have achromatopsia only see the world in shades of grey, black and white.
There are different types of colour blindness and in extremely rare cases people are unable to see any colour at all, but most colour blind people are unable to fully 'see' red, green or blue light.
Achromatopsia affects an estimated 1 in 30,000 people worldwide. Complete achromatopsia is more common than incomplete achromatopsia. Complete achromatopsia occurs frequently among Pingelapese islanders, who live on one of the Eastern Caroline Islands of Micronesia.
Cyanopsia is a medical term for seeing everything tinted with blue. It is also referred to as blue vision. Cyanopsia often occurs for a few days, weeks, or months after removal of a cataract from the eye. Cyanopsia also sometimes occurs as a side effect of taking sildenafil, tadalafil, or vardenafil.
Some color blind users are lacking the capability to detect the lower color wave frequencies associated with red. For these users, red color waves read as "no signal", or "black". These users confuse red and black, so this contrast should be avoided whenever possible.
People who are color blind see normally in other ways and can do normal things, such as drive. They just learn to respond to the way traffic signals light up, knowing that the red light is generally on top and green is on the bottom.
Browns, oranges, shades of red and green are easily confused and people with both types will also confuse some blues with some purples and struggle to identify pale shades of most colours. However, there are some specific differences between the two types of red/green deficiencies.
Help your child understand color by relating it to her other senses. You might describe red as a hot, loud color; white as smooth and quiet; black as shiny; or blue as the notes of a saxophone. A blind blogger once wrote: Yellow is buttery and rich, like sunshine on your face.
A person with protan type color blindness tends to see greens, yellows, oranges, reds, and browns as being more similar shades of color than normal, especially in low light. A very common problem is that purple colors look more like blue.
There's no cure, but special glasses and contact lenses can help. Most people who are color blind are able to adjust and don't have problems with everyday activities.
Use a colorblind-friendly palette when appropriate
For example, blue/orange is a common colorblind-friendly palette. Blue/red or blue/brown would also work. For the most common conditions of CVD, all of these work well, since blue would generally look blue to someone with CVD.
Shockingly, being colorblind has its advantages. The University of Edinburgh discovered that individuals with red-green colorblindness are better at seeing camouflage. Color can actually impede our ability to detect patterns and textures.
Monochromacy. Monochromacy is often called total color blindness since there is no ability to see color.