Key points
- Colour blindness is a genetic condition that affects more men than women.
- Certain colour combinations make details invisible for colour blind people.
- Using accessible colours to visualise science data enhances understanding and reduces bias and misunderstanding.
Dr Mark Lindsay was five years old when he first learned that tree trunks were brown.
“Up until that point, I believed leaves and trunks were all green. Just lighter and darker shades," Mark said.
Mark had discovered he was colour blind. Colour blindness, or colour vision deficiency (CVD), is a visual impairment that affects an individual's ability to perceive certain colours accurately.
Mark is now a geologist. He inherited his colour vision deficiency from his grandfather. In a twist of fate, his grandfather was also a geologist!
To succeed in science, Mark has learned not to make assumptions about his view of the natural world. Instead, he's constantly aware that everyone sees things differently.
A hidden handicap
The primary cause of colour blindness is the absence or malfunction of photoreceptor cells in the retina, known as cones.
Cone cells are responsible for detecting light and colour. They come in three types: red, green, and blue. Each type is sensitive to a specific range of wavelengths. The brain interprets various colours based on the signals received from cone cells.
Colour blindness typically results from a genetic mutation that affects one or more of these cone types. And men are more frequently affected than women.
The most common types of colour blindness are:
- Deuteranomaly (red-green colour blindness). The most common form of colour blindness, deuteranomaly affects the green cone cells. People with deuteranomaly have difficulty distinguishing between red and green hues.
- Protanomaly (red-green colour blindness), affects the red cone cells. People with this type struggle to differentiate between red and green colours.
- Tritanomaly (blue-yellow colour blindness) which is caused by the malfunction of blue cone cells. This affects the ability to perceive blue and yellow colours, and
- Monochromacy (complete colour blindness), a rare condition which occurs when an individual has only one type of cone or no functional cones at all. This means they see the world in grayscale.
Colour perceptions
While people with normal vision can see a visual symphony of colourful vegetables in the image above, the perception is somewhat different for colour-blind individuals.
Using a colour blindness simulator, we get a sense of how people with different types of colour vision deficiency perceive the same picture.
The same picture of colourful vegetables is shown using filters for different types of colour vision deficiency. Top left image shows deuteranomaly (red-green colour blindness). Top right shows protanomaly (red-green colour blindness). Bottom left shows tritanomaly (blue-yellow colour blindness). Bottom right shows monochromacy (complete colour blindness). These images were generated using Pilestone's colour blindness simulator.
A world of unseen data
Scientists work to make the unseen seen. To do this, they use an array of strategies to visualise scientific results and concepts.
Conveying complex data is tricky. Often, the most effective approach is using coloured visualisations. The detailed visual data presentations common in science often fail to accommodate those with colour blindness, rendering some information effectively invisible to them.
Imagine a climate change map depicting temperature variations through a gradient of colours. For someone with colour blindness, these variations aren't evident; the design effectively blocks them from ‘seeing’ the data.
This scenario extends to diverse scientific fields. From astronomy to medicine, colour-coded information is integral to conveying patterns, trends, and anomalies. And the implications extend far beyond inconvenience. A researcher could misinterpret data due to a rainbow colour gradient. Or a physician could misdiagnose a condition because they lose critical information in the chromatic shuffle.
The rainbow conundrum
Rainbow-like and red-green colour maps are top offenders for accessibility. While visually appealing, these colour schemes pose challenges for people with colour blindness.
The uneven distribution of colours and the dominance of certain hues can lead to misinterpretations, affecting the accuracy of scientific conclusions.
For example, bright yellows and subtle greens may morph into an undecipherable palette for some colour-blind individuals. This can erase nuances in crucial data.
Making data accessible and inclusive
With many journals requesting colour blind-friendly scientific illustrations, what can we do to make colour-coded science data more accessible?
“Colour palettes used in charts and figures cause the most confusion for scientists,” Mark said.
Black and white is the safest option. But sometimes, colour is king.
"To be colour-blind sensitive, avoid using red and green together. Use contrast to ensure your text and background colours are easy to read. Also consider using icons or symbols instead of coloured text labels for your data points."
Software is also providing solutions.
“A lot of software used for data visualisation now have options to adapt to, adjust for or accommodate a range of colour vision deficiencies. Thankfully, many palettes for the colour-blind are offered by the major software packages in Python, R and Matlab,” Mark said.
When in doubt, Mark recommends you check it out using a colour-blindness simulator.
Seeing on the spectrum
The beauty of science lies not just in what we see but in our collective ability to make the unseen visible.
“Educating people to consider colour accessibility when communicating data and concepts is a great first step,” Mark said.
“By considering the challenges posed by colour blindness in science we begin to break down barriers. We also enrich the scientific narrative by enabling more diverse perspectives.”