Data Visualisation Workshop - Colour

EPA Victoria - June 2018

Dr James Baglin, School of Science, Mathematical Sciences, RMIT University

Last updated: 24 June, 2018

What is Colour?

  • Colour is our visual perception system’s response to the visible spectrum of light. Visible light is electromagnetic radiation emitted in wavelengths between 400 - 700 nm.
  • Light outside this range is not visible to the human eye and include the infrared range (700 nm to 1 mm) and the ultraviolet range (10 - 400 nm).

“Rendered Spectrum” by Spigget - Own work. Licensed under CC BY-SA 3.0 via Commons.

What is Colour Cont.

  • Within the visible light range there are three primary colours that photoreceptors (cones) within our eyes’ retinas can respond to, hence humans are said to be trichromatic. These colours include blue, green and red.

“RGB illumination” by en:User:Bb3cxv under CC BY-SA 3.0 via Commons.


Cardinal Colour Rules

HSV Colour Naming

Colour Scales

Colour Scale Selection

  • Cynthia Brewer developed the ColorBrewer palettes to promote best practice in map representation.
  • However, her work applies to all data visualisation.
  • Select effective colour palettes based on:
    • Sequential
    • Diverging
    • Qualitative data
    • Single or multi-hue
  • Colour-blind and print-safe palettes
  • Web tool - http://colorbrewer2.org/

Colour Blindness

Colour Associations

  • Colours also have associations (MacDonald 1999).
Colour Positive Association Negative Association
Red Passion, strength, energy, heat, love Blood, war, fire, danger, anger, aggression
Green Nature, spring, fertility, safety, environment Inexperience, decay, envy, misfortune
Yellow Sun, summer, gold, harvest, optimism Cowardice, treason, hazard, illness, folly
Blue Sky, sea, stability, peace, unity, depth Depression, obscenity, conservatism, passivity
White Snow, purity, peace, cleanliness, innocence Cold, clinical, surrender, sterility, death, banality
Gray Intelligence, dignity, restraint, maturity Shadow, concrete, drabness, boredom
Black Coal, power, formality, depth, solidarity, style Fear, void, night, secrecy, evil, anonymity


Activity 3

  • Working with a partner or in a small group, view the following the data visualisations by clicking on the link:.

    1. Omega Age Chart by Wikipedia User, The Green Hood
    2. Age Distribution of Religious Groups by Pew Research Center
    3. Gun Deaths in Australia by Andy Kiersz

  • For each visualisation, discuss how colour is being used and whether you think it is being used effectively.

Quick Quiz

References

MacDonald, L. W. 1999. “Using color effectively in computer graphics.” IEEE Computer Graphics and Applications 19 (4): 20–35. doi:10.1109/38.773961.