Colour with a purpose
Colour should do one clear job: separate categories, show order, show direction from a midpoint, or highlight one item. The message must still work without colour.
Colour has four distinct jobs (W6 pp. 21-23):
| Job | Design | Example |
|---|---|---|
| Categorical identity | Distinct hues, no implied order | Computing 40, Physics 25, Math 35 |
| Ordered values | Pale to strong of one hue (sequential) | Course A 10, B 30, C 60 |
| Direction around a midpoint | Two hues diverging from a neutral zero | Change -10, 0, +15 |
| Focus | One accent colour, the rest grey | Computer vision highlighted among three courses |
Mismatches mislead: a sequential ramp on unordered subjects implies a ranking; a rainbow on ordered values hides the order; a diverging scheme needs a meaningful midpoint such as zero change.
Would the message survive without its colours? (W6 pp. 20-21). Roughly 1 in 12 men and 1 in 200 women have some colour-vision deficiency, and slides are often printed or projected in poor light. Encode identity redundantly: names such as "Cohort A" rather than "Teal series", direct labels, distinct marker shapes or line styles, and enough contrast. Check every chart in grayscale and at classroom size; a label always accompanies colour.
Source: W6 PDF pp. 1-37. Most numbers in the lecture are illustrative or constructed for teaching; pp. 26-27 reuse the Week 5 synthetic registration counts. The Week 6 lab manual (L6) practises Week 5 EDA reasoning and is worked through section by section in Lab work.
Practice problems
Supplementary study questions on the lecture concepts — not verbatim exam questions. Each answer counts toward spaced review.
1. Conceptual understanding
Definitions and distinctions.
Which colour scheme suits values ordered from small to large?
How should two series be identified so the chart still works in grayscale?
2. Application
Apply the concept to a case or calculation.
Computing, Physics and Math bars need colours. Which choice fits?
Changes of −10, 0 and +15 registrations. Which colour design fits?
3. Interpretation and limitations
Evaluate assumptions and justify conclusions.
How do you make one course easy to find among three?
Which check does the lecture recommend for every chart?
Explain it in writing
Self-checked, not marked. Write a few sentences, then compare with the example answer. Your writing is saved as you type.
Show an example answer
Give them names such as Cohort A and Cohort B, use different marker shapes or line styles, and label the lines directly, so that identity no longer depends on hue.
Check: did you answer the question, use evidence or working, and avoid claiming more than the evidence supports?
Show an example answer
When values move in two directions from a meaningful midpoint, such as changes above and below zero. A neutral colour marks the midpoint.
Check: did you answer the question, use evidence or working, and avoid claiming more than the evidence supports?