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Can colorblind people see black on red?

Colorblindness, also known as color vision deficiency, is the decreased ability to see color or differences between colors. It affects approximately 1 in 12 men and 1 in 200 women worldwide. There are different types of colorblindness that cause people to have trouble distinguishing certain colors.

What is Colorblindness?

Colorblindness occurs when there is an abnormality in the color-sensing cones in the eye. Normal human eyes have three types of cones that detect light: red cones, green cones, and blue cones. The cones work together to detect the full spectrum of colors.

In colorblind people, one or more of the cone types is absent or not functioning properly. This results in an inability to distinguish some colors, especially reds, greens, browns, oranges, yellows, and blues.

The most common types of colorblindness are:

  • Red-green color deficiency – red and green cones don’t detect enough differences in light
  • Blue-yellow color deficiency – blue cones don’t detect enough differences in light
  • Complete color blindness (monochromacy) – inability to see any color, very rare

Colorblindness is usually an inherited genetic condition. The genes that control the color-sensing cones are carried on the X chromosome. Since men only have one X chromosome, they are more likely to have color vision deficiencies if that chromosome carries an abnormal cone gene.

Can Colorblind People See Black on Red?

The ability for colorblind people to distinguish black text or images on a red background depends on the type and severity of their color vision deficiency.

Red-Green Color Deficiency

People with a red-green color deficiency (the most common forms being protanopia and deuteranopia) have trouble distinguishing between reds, greens, and shades in between. They see reds and greens as more muted or grayish in appearance.

However, most people with a red-green deficiency can still see bold primary colors. So they would likely be able to differentiate black text or images on a bright red background.

The main issues they may have are:

  • Distinguishing dark red from black or dark gray
  • Differentiating shades of red, which may all look brownish

Here is a simulation of how black text on red would appear to people with protanopia and deuteranopia:

Normal Vision Protanopia Deuteranopia
Black text on red background with normal color vision Black text on muted red background with protanopia Black text on muted red background with deuteranopia

As you can see, the black and red are still distinguishable but the shades of red are desaturated.

Blue-Yellow Color Deficiency

People with blue-yellow color deficiency have difficulty distinguishing blues from greens and yellows from pinks or reds. However, they generally have normal perception of bold primary colors.

Since a bright red contains no blue components, people with a blue-yellow color vision defect should still be able to see it as vivid red. And the contrast between black and red should be very clear.

Some people with mild forms like tritanomaly may have trouble differentiating darker burgundy reds from black. But bright scarlet reds should stand out against black.

Complete Color Blindness

People with extremely rare complete color blindness (monochromacy) can only see shades of gray ranging from black to white. So they cannot distinguish any colors at all.

For someone with complete color blindness, black text on a red background would appear as black text on a gray background. So there would be very little contrast between the colors.

Some people with monochromacy can detect shades of blue if the light is bright enough. But in general, black on red would be very hard to read.

Tips for Making Visuals Accessible to Colorblind People

Here are some tips to help make images, text, and designs viewable for people with various types of color vision deficiencies:

  1. Avoid color combinations like red-green, green-brown, blue-purple, green-blue, or light green-yellow
  2. Use high contrast colors – black or dark colors on a white or light background
  3. Don’t convey information with color alone. Use shapes, patterns, or labels.
  4. Allow users to customize color settings on apps and websites.
  5. Add symbols or labels to colored sections in charts or graphs.
  6. Make sure text and important elements have good contrast from background.
  7. Ask people to test your designs and give feedback.

By keeping these tips in mind, you can help make your designs inclusive for the colorblind population.

Special Glasses for Colorblind People

There are glasses available to help some types of colorblind people distinguish certain hues. They work by blocking out wavelengths of light that correspond to areas of weakness.

Here are some examples of colorblindness correction glasses:

  • EnChroma glasses – blocks specific wavelengths to enhance red-green perception.
  • Oxy-Iso glasses – blocks excess light to sharpen blue-yellow perception.
  • Iristech lenses – uses a notch filter for specific colorblindness types.

These glasses primarily help with moderate forms of red-green or blue-yellow color deficiencies. They allow people to discern more shades and faint colors.

The glasses are not effective for severe colorblindness or complete color blindness. But they may provide some enhancement for distinguishing colors like black and red.

Other Assistive Technologies

People with color vision impairments can benefit from using computer and phone accessibility settings. These allow adjusting colors and contrasts to make things easier to see.

Some examples include:

  • Inverted color filters – switch background and foreground colors
  • Color correction filters – adjust gamma, hue, saturation
  • Grayscale mode – switch screen to shades of gray
  • Font and size adjustments – bold text options, zoom functionality
  • Color identification apps – scan and identify colors

Braille labels or tactile indicators can also be used to denote colors for people with complete color blindness.


The ability to distinguish black on red varies significantly depending on the type and severity of color vision deficiency. While people with common forms like red-green color blindness can generally see bold primary colors, those with complete color blindness see no colors at all.

Creating accessible designs with high contrast and multiple indicators is important to accommodate the full spectrum of color vision. Assistive technologies like specialty glasses and computer settings can also enhance the ability to differentiate colors.

Understanding the perspectives of people with different types of color vision can help us build a more inclusive world that provides access to information for everyone.