How to make figures and presentations that are

friendly to color blind people

Masataka Okabe and Kei Itowith special thanks to

Cahir O’Kane

“How common is color blindness? ”

One in twelve males (8%) is red-green color blind.

Type 1 (protanopes) and type 2 (deuteranopes): functional defects in red and green cone cells, respectively.

People with defects in blue cone cells (type 3: tritanopes) are relatively rare (one in tens of thousands.)

Red-green color blindness is commoner than AB blood group. There should be more than TEN color blinds in the room with 250 people !

“Can color blind people see colors? Do they see everything black and white? ”

non color blind

protanope (red cone cells defective)

deuteranope (green cone cells defective)

tritanope (blue cone cells defective)

Color blindness is not a total loss of color vision. But certain ranges of colors are hard to distinguish.

Double-staining withred and green signals.

Not understandable for color blind people !

protanope (red) deuteranope (green) tritanope (blue)

“How can you see this color ? ” (common question ;-)

Let’s simulate how color blind people see this.

A typical confocal picture

“Another problem: recognition of double positive — cannot distinguish yellow from green”

This appears like…

protanope (red) deuteranope (green) tritanope (blue)

“How can you make double staining understandable both for color blind and for

non-color blind people ? ”

Not good. Then…

1. Present grayscale pictures of each channel.2. Don’t use red. Use magenta (purple) instead.

red-green double staining

In magenta-green pictures, double positive area becomes white.

magenta-green double staining

How to convert red channel to magenta?Let’s try with Photoshop.

How to convert red channel to magenta?REVIEW

red channel�-1select all�-Acopy�-C

blue channel�-3

paste�-V

all channel �-~ or -0�

original

Just type “ - 1AC3V~”� !

“Single labeling should be OK !”

not so...protanope deuteranope tritanope

Some colors are very difficult to see. (especially red pictures for protanopes.)

“Even if you don’t care about color blinds...”

Can you convey more information by making it color ?It should not be just for aesthetic purposes.If you just want to show what kind of label you used (GFP, Cy3, etc.), a sentence in the figure legend might be enough.

Monochrome is the best for tonal

reproduction !

when printed Pure green and red are out of gamut (printable color range). Subtle gradation will be lost

in the published paper. (especially in the area

with the strong signal.)

“How about triple labeling? ”

1. Present grayscale picture of each channel.

Good Question…

Don’t show the combined picture only. Please:

2. Assign dispensable “background staining” to red.

“Which is better ?

Faster to relate colors to channels. (Slides?)

Better tone. Easier to compare staining patterns.(papers and posters?)

green blue red

“How about characters and drawings? ”

1. Cannot distinguish different colors.Especially drawings and graphs with red, orange, yellow, yellow green and green symbols and lines.

Three problems that color blind people suffer:

2. Fail to see some objects.Red or magenta symbols and thin lines over dark blue background.

3. Difficulty in seeing emphasized parts.Red or green characters in white text over dark blue background.Red characters in black text over bright background.(Red appears similar to black…)

“How to make slides and figures? ”

4. Avoid simultaneous use of red and green.

hemmingeg.

vermilion hatchingpure dark red

3. Avoid small red objects. Since protanopes cannot detect long wavelengths, red appears darker. It is hard to recognize red objects above black, blue or green backgrounds. When red is unavoidable, avoid dark red. Use vermilion, put hatching, or add a hem.

2. Over blue or black background, use only yellow and white characters. Emphasize with monochromatic effects like fonts, italics, hatching, shadows shadows or changing brightness.

1. Mainly use black, blue, white and yellow. Keep the number of colors to a minimum.Use combinations of different symbols with a few, vivid colors rather than a single symbol with various colors.

vs.

“Anything else? ”

“Cannot see red laser pointer well…”

Green laser pointer is good for color blind people.

The same also for non-color blinds.

Conclusion

There are always color blind people among the audience, readers and referees. Please take this into account when preparing your presentations

(papers, slides, web pages etc.)

Thank you for your cooperation !

Acknowledgements: Michina Shiraki (double- and triple-staining pictures)Kenji Kitahara and Makiko Ohkido (ophthalmology issue)