Colour Scales and Colour Maps

Learn about colour scales

categorical colourmap

appropriate for categorical data, always segmented

categorical colourmap rule of thumb 1

limit to 6-8 colours, especially if regions are not contiguous

categorical colourmap rule of thumb 2

use easily distinguishable colours

categorical colourmap rule of thumb 3

be consistent in your colour mappings across different views

categorical colourmap rule of thumb 4

consider the contrast against the background colour and black and white

ordered colour maps

appropriate for either kind of ordered data and can be sequential or diverging

sequential colour maps

from a minimum value to a maximum value

sequential colour map options

luminance only, luminance with hue, saturation only, saturation with hue

diverging colour maps

two hues at the endpoints with a neutral colour as the midpoint

segmented vs continuous colourmaps

segmented emphasise discrete nature of ordinal data and continuous emphasise continuity in quantitative data

rainbow colour map advantage

specific subranges can be easily named, e.g., red or yellow in contrast to more yellow

rainbow colour maps disadvantage 1

hue is used to indicate order which violates the expressiveness principle

rainbow colour maps disadvantage 2

the rainbow colourmap is not perceptually linear

what is better than a rainbow colour map?

monotonically increasing luminance colour map - multiple hues for semantic categories