What Is Color Blindness?

A DESIGNER’S GUIDE TO COLOR BLINDNESS Designed Written Alex Villagomez i FOREWORD 02 WHAT IS COLOR BLINDNESS? 04 COLOR BLIND VISION 08 LIKELIHOOD OF HAVING CVD 10 ARE YOU COLOR BLIND? 12 RELEVANT THINGS TO CONSIDER 14 THE DESIGN PROBLEM 16 WHY YOU SHOULD CARE 18 PROBLEMATIC COLOR COMBINATIONS 20 SUGGESTED USE OF COLOR 22 CONTRAST IN COLOR 24 PLACEMENT AND LAYOUT 26 PATTERNS AND OTHER ELEMENTS 28 THE COLOR BLIND DESIGNER 30 ADDITIONAL METHODS OF COPING 32 QUICK REFERENCE 34 SOURCES FOREWORD This manual has been created to aid designers in making design de- cisions in regards to their projects while being mindful of color blind viewers. As a color blind designer, I would like to raise awareness to the condition that affects millions of people in the U.S. alone. My hopes are that designers worldwide can create design that eases the lives of people with color blindness and removes most, if not all, of the ambi- guity we face that can affect our lives severely. 02 Red-Green Axis (a) WHAT IS COLOR BLINDNESS? The inability to perceive color vision at its fullest is known as Color Vision Disorder. This, however, does not mean that every person with CVD cannot see color at all. In fact, only a small percentage of people who are color blind are truly blind to all color, with vision that only allows for shades of gray. Only they can truly live up to the term ‘color blind’. The acceptable term to refer those who are not blind to all color is ‘color deficient’. People with color deficiency have a difficult time distinguishing certain colors. The severity of their ability to differentiate between colors depends on the individual. Inside the retina of the eye exist millions of cone-shaped color receptors, alongside rod-shaped light receptors (Bailey). There are three different kind of color receptors, one for each of the colors that make up all colors in the visible spectrum. These receptive cones correspond to different wavelengths of color: Blue-Yellow Axis (b) (b) Axis Blue-Yellow short (blue), medium (green), and long (red) (Facts About Col- or Blindness). When a person is color blind, one or more of the cones inside their eyes is abnormal, preventing them from seeing that specific color at its fullest. These cones can either be shifted or missing. When the cone is only slightly shifted, vision pertaining to that color wavelength is still visible, but only slightly. When the cone is not present, neither is that color. This is a simplified representation of the Lab Color Space model with Luminosity set at 50%. Luminosity controls the lightness of the color, while the ‘a’ and ‘b’ axes control the red-green and blue-yellow color tandems, respectively. An important thing to understand is that Color Blind Deficien- cy is typically categorized into congenital and acquired. Con- genital color blindness affects people through a recessive gene trait, whereas acquired color blindness occurs due to injury or results from an illness. Acquired Color Vision Defects can occur through chronic illnesses such as Alzheimer’s disease, diabe- tes mellitus, glaucoma, leukemia, liver disease, chronic alco- holism, macular degeneration, multiple sclerosis, Parkinson’s disease, sickle cell anemia, and retinitis pigmentosa (Acquired Colour Vision Defects). Additionally, people may lose color vision through accidents that damage the retina or the brain, medications with side-effects, harmful chemicals, and age (typically over-exposure to the sun) (Tritanomaly/Tritanopia). 04 Condition COLOR BLIND VISION Present Shifted Missing A human with normal color vision can see about 1 million dis- tinct shades of color. For someone with color blindness, the appearance of certain color hues is reduced; they can only see part of the full color gamut (Tritanomaly/Tritanopia). For Normal persons with tritan-type deficiency, the loss mainly affects the Red Vision Protanomaly Protanopia “blue-yellow” axis of color space while leaving the “red-green” Long axis intact. Obversely, protan and duetran-type deficiencies are grouped together because they affect the same color axis (red- green). A person incapable of seeing a full range of red will have diffi- Normal culty detecting the red in a color composed of it. For example, Green Vision Duetranomaly Duetranopia the color violet is a mixture of blue (short wave-length) and Medium red (long wave-length). A person with Protan-type deficiency will most likely see blue only, depending on the severity of the Wavelength cone distortion. When violet is placed next to blue, blue-violet and slightly different shades of violet, differentiating the colors may be impossible. Normal Blue Vision Tritanomaly Tritanopia Short The different types of color blind vision are classified by the color the viewer cannot see and classified again if the cone is shifted or missing. Above is a chart categorizing the different types of disorders. Anatomy of Human Eye Ciliary Body = Cones = Rods Sclera Cornea Iris Retina The eye functions much like a camera and vice versa. Light comes through the lens and into the back where it hits the retinal wall. The light is then absorbed by light and color receptors which form a carpet-like layer inside of the retina (In the Eye | Causes of Color).. When a person is color blind, some of their cone shaped color receptors will be either missing or tilting away from the light source. Optic Lens Nerve Pupil Fovea Anterior Chamber Vitreous Body 08 X-Linked Recessive Gene Inheritance LIKELIHOOD OF HAVING CVD The recessive gene for color blindness is carried in the X chro- X X mosome (Bailey). Since women are born with two X chromo- Y X somes (men have one X and one Y), they have a higher chance of compensating for the color blind trait that may have been inherited. This means men have a lesser chance of combating the trait and therefore are more likely to be affected by color blindness. It is quite common to see a mother pass down her Unaffected Father Carrier Mother color blind trait to her son, and have normal vision herself. Likewise, the mother’s male siblings can all be color blind. X X X X The probability of a male having any degree of color blindness Y X X Y is 8%, where only .5% of women are affected (Types of Colour Blindness). Approximately 1% of those men are deuteranopes, 1% protanopes, 1% protanomalous and 5% deuteranomalous. Nearly half of color blind people will have a mild anomalous deficiency (slightly shifted cone), the other 50% have moder- Unaffected Son Unaffected Daughter Carrier Daughter Affected Son ate or severe anomalous conditions (severely shifted or missing cone). Tritanopia, Tritanomaly, and Achromacy (absence of all color) are extremely rare, affecting less than 1 out of 30,000 Unaffected Affected Unaffected people (Types of Colour Blindness). X X Chromosome X X Chromosome Y Y Chromosome Digging even further, these figures rise in areas where there is a This is an example of the likelihood of parents of four children passing greater number of white (Caucasian) people per head of popu- on the recessive color blind trait, which is located in the X-chromosome. lation, so in Scandanavia the figures increase to approximately 10-11% of men. By contrast, in sub-Saharan Africa there are few color blind people. Countries such as India and Brazil have a relatively high incidence of color vision deficients because of the large numbers of people with mixed race genes in their genetic history (Types of Colour Blindness). 10 Ishihara Plate Test ARE YOU COLOR BLIND? If your family has a history of color blindness, especially through uncles and grandfathers, your chances of either being color blind or carrying the trait are very high. A regular check up with your optometrist will determine whether you have a color deficiency. You will be asked to take a series of visual tests called Ishihara plates, which contain a randomized number of dots that vary in color and size. Within the dots is a figure of a number or letter that is visible to a person with normal color vision, but difficult to distinguish or simply hiding in plain sight to a person with CVD. To test yourself online for color blindness, visit: enchroma.com/test/instructions/ Can you identify the number within this Ishihara test? If not, then you are affected by red-green color blindness. Graphic generated at franciscouzo.github.io/ishihara/ 12 RELEVANT THINGS TO CONSIDER The majority of people with Color Vision Disorder live normal lives and see their abnormality merely as a small hindrance. This is especially true for those who only have shifted cones. Even though the majority of people have normal color vision, everyone will see color slightly different. Color can also look much different to someone in the dark than it does in bright light (similar to the cones perceiving color, the rods in the retina help perceive color in different light). Driving, however, is one important day-to-day activity that is reliant on color. Street lights, signs, brake lights, and emergency vehicles are red, making it difficult for people with red-green color blindness to see. Some countries such as Romania and Tur- key even restrict Protanomalists from driving at all. Becoming an airplane pilot is also an occupation that requires perfect col- or vision. In the past, anyone with full or partial color blindness was disqualified from joining the U.S. military (Newsweek). Other day-to-day activities that are difficult for people with CVD include: noticing sunburns, knowing when food is proper- ly cooked, finding objects in a field of grass, and selecting fruits that are ripe.

Load more