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AB
Figure 1. Color presentation styles. (A) Pie chart: difficult to quantify because the size of the red pie ACKNOWLEDGMENTS
slice is not specified and the ledgend is inscrutably small. (B) Colors in (A) are almost indistinguish-
able to people with RG-CVD. (C) The same data are clear to all in an annotated bar chart.
PREPARING IMAGES FOR ALL
TO SEE
Assistive technologies notwithstanding,
there is no substitute for well-designed
illustrations. Whether destined for presen-
tation or publication, images should always
be tested using vischeck.com, color-
blindness.com, colorbrewer2.org, contrast-
checker.com, Sim Daltonism, Adobe
Illustrator, etc. An extensive literature
review is beyond the scope of this article,
but we here summarize the most frequently
cited best practices for publication, presen-
tation, and instruction:
1. Select graphic styles for accessibility:
Figure 1 shows two presentation styles.
The pie chart (A) is difficult to quantify
and the legend is inscrutably small.
(B) Colors in (A) are almost indistin-
guishable to people with RG-CVD.
The same data are clear to all in an
annotated bar chart (C). On GSA’s web
page www.geosociety.org/documents/
gsa/about/MbrDemographics.pdf, the
Professional Interests chart is clear to
all but the Employment Type chart is
totally illegible to some. Numerous
other good and bad examples can be
found via Google.
2. Redundancy: Distinguish items by
more than color. Use circles and
squares and solid and dashed lines.
Label items directly, not in a key.
3. Color choice: Colors differing only in
hue, especially percentage red or green,
cause problems. Dark red–dark green,
blue–violet, red–orange, and yellow–
green confusion is common. Magenta
and turquoise are good choices because
people with RG-CVD can see the blue
component.
4. Thickness, brightness, and contrast:
People with RG-CVD cannot see thin
lines or small polygons because insuf-
ficient functioning retinal cones are
activated. Make lines thick and use
high-contrast text, arrows, or other
C to individuals with CVD will look better to
shapes. Drop-shadows and boxes make
text stand out. Saturation and bright-
ness variations are critical.
5. Avoid rainbow color maps: Despite
copious research showing that it is the
worst possible choice (e.g., Light and
Bartlein, 2004), the rainbow color map
continues to be popular (Borland and
Taylor, 2007). Although violet and red
are the extremes of visible light, they
do not convey different magnitudes to
the brain. A diverging color map does
(http://www.kennethmoreland.com/
color-maps/).
PRESENTING AND INSTRUCTING
In addition to preparing illustrations
well, a presenter’s words, gestures, and
actions are important. Individuals with
RG-CVD commonly cannot identify col-
ors, even if they can distinguish them.
Instead of referring to a “pink curve,” say
“the pink, dashed curve at top left.”
Red laser pointers are extremely diffi-
cult for some to see (Okabe and Ito, 2008).
Green ones are superior (conference orga-
nizers please note!) and are also good for
pointing to stars and planets.
DISCUSSION AND CONCLUSIONS
Gene therapy offers hope for a cure
(Gudgel, 2015; Saey, 2016), but for the
foreseeable future, RG-CVD will remain
prevalent. Government agencies have
Section 508 Standards including guidelines
for CVD-compliant documents. See, for
example: section508.va.gov, colorusage.arc
.nasa.gov/indiv_diffs.php, and nws.noaa
.gov/sec508.
People with CVD typically prefer black
and white to color. In fact, in his 1982
album, Concert in Central Park, Paul Simon
changed the “Kodachromes” lyrics to
“everything looks better in black and white.”
However, we must recognize that trichro-
mats will continue to prefer color whenever
available. The key is to design for inclusiv-
ity. Color images crafted to be clearly visible
www.geosociety.org/gsatoday
everyone. To continue the discussion, please
visit: http://www.theiagd.org/resources/
color-vision-deficiency.
We thank Rick Murray of Boston University
and two anonymous reviewers for very useful
suggestions. Our research was supported by NSF
DUE 1323419.
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MANUSCRIPT RECEIVED 6 OCT. 2016
REVISED MANUSCRIPT RECEIVED 11 DEC. 2016
MANUSCRIPT ACCEPTED 14 DEC. 2016
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