Colours
Colour spaces and colour use
Wednesday, 18 March 2026
Introduction
Colours
Learning objectives
- Know about colour spaces - RGB and HCL
- Use fewer colours
- Finding the right palette
- Choose a palette for your project
Perception of colours
Human vision
- Perception of light/dark contrasts
- Yellow/blue contrasts
- Green/red contrasts
Three types of color receptors
RGB - Red Green Blue
The most commonly encountered color system.
Hexadecimal notation allows 16.7M colors
- Red #FF0000
- Blue #00FF00
- Green #0000FF
System is additive, e.g. the maximal value #FFFFFF corresponds to white.
HCL - Hue, Chroma, Luminance
HCL scales are limited
| Parameter | Start | Range |
|---|---|---|
| Hue | 0 | [0-360] |
| Chroma | 0 | [0-360] |
| Luminance | 0 | [0-360] |
Choosing colours in HCL space
Color and context
Why is this not the default?
But this?
Palettes and their use
Types of palettes
Popular color spaces
Brewer
Viridis
Jet (Python)
Viridis color spaces (palette)
Qualitative palettes
Use for unordered categorical data
- Lighter colours (high luminance) are less distracting
- Flashy colours are needed for points or lines
Sequential palettes
- Ordered categorical data (choice of
n) - Binned numerical data
Sequential palettes
- Ordinal data (choice of
n) - Numerical data
Diverging palettes
- Opposing values
- Few samples with high and low scores
- Examples:
- Correlation \(r^2 [-1, 1]\)
- Bimodal distributions
How colors are selected
Choosing a color-blind friendly palette
All colors
viridis design
Tip
The colorBlindness package can render your palette in this fashion.
Too many colors
Continous, rainbow palette
Binning and another palette
Focusing on a few important points
Preferred - scatter plot
Developing a suitable color scheme
Taylor Swift
How to create a custom palette
colorspace package
HCL Picker and HCL wizard
