FES 720 Introduction to R
Using Colour
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FES 720: Intro to R
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“avoiding catastrophe becomes the first principle in bringing color to information: Above all, do no harm.”
Envisioning Information, Edward Tufte, Graphics Press, 1990
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Using Colour
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Physics of colour
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Practicalities of colour
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Accessibiilty of colour
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1. Physics of Colour
Colour is ‘visible light’
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Describing colour
1. Hue, lightness, and colorfulness
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Describing colour
2. RGB
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Background matters
Colors look darker and smaller against white and lighter and larger against black.
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Use a consistent background colour
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Avoid gradients of colour
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Avoid any other variation in background colour
Simultaneous contrast can make the same colors look different
Simultaneous contrast can make different colors look the same
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Ensure background contrasts with text and data colours
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Light (e.g., white) and low colourfulness colours (pale greys, creams, etc).
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If using colours to highlight text (e.g., heatmaps) ensure enough contrast.
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2. Practicalities of Colour
Use color to communicate information
Colour !- decoration / wallpaper.
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Different colors should correspond to different meanings
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Three main uses of colour to promote communication
• To highlight particular data
• To group items (categories)
• To encode quantitative values (sequential or diverging)
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Use soft, natural colors to display most information and bright and/or dark colors to highlight information
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Use colours of the same hue to group/categorise data
Fig A example categorical map from the US census of 2000.
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Use colours of increasing/decreasing brightness or colorfulness to illustrate quantitative data
Sequential
Fig. A map of precipitation with a sequential lightness-hue ramp from climate.gov.
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Use colours of increasing/decreasing brightness or colorfulness to illustrate quantitative data
Diverging
Fig A map of temperature anomaly form climate.gov.
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Use light colours for non-data components
| Component | Default Color |
|---|---|
| Axis lines | Thin gray lines of medium intensity. |
| Borders | If needed, thin gray lines of medium intensity. |
| Background | Use white or ‘None’ |
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Some suggestions for data components of graphs
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Use distincts hue of medium intensity for each data series.
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For small data points or thin lines, use distinct hue of high intensity.
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For larger data points or wider lines, use distinct hues of medium intensity.
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3. Accessibility of Colour
Red-green colourblindness affects:
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about 8% of the male population and
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0.5% of the female population
Use colour and symbols
Keep colours minimal
Avoid problem colour combinations
See: http://blog.usabilla.com/how-to-design-for-color-blindness/
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Use colorbrewer to help with everything!
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References
Few, S. 2008. Practical Rules for Using Color in Charts
MacDonald, L.W. 1999. Using Color Effectively in Computer Graphics
https://betterfigures.org/2015/06/23/picking-a-colour-scale-for-scientific-graphics/