← ACARA Digital Technologies Years 5–6

A colour key: whole numbers stand for colours

A list that matches each whole number to a colour, like 1 = red, 2 = blue and 3 = yellow, so a grid of numbers can show a picture.

Part of: ACARA Digital Technologies Years 5–6 — Representing Data with Numbers — Module 20

Understanding A colour key: whole numbers stand for colours in ACARA Digital Technologies Years 5–6

What it does: The key tells us that 1 means red and 2 means blue, so the row of numbers becomes a row of coloured squares. If 3 means yellow everywhere, anyone decoding the grid will get the colours right. Changing the key halfway would mix up the picture. A colour key is a list that says which number stands for which colour, like 1 = red. Look up 2 in the key: 2 = blue. Each colour needs its own number. If three colours share the number 1, we can't tell them apart. Keep the same key for the whole picture. If the key changes, the numbers give the wrong colours.

Common mistakes: Each colour needs its own number. In this key 1 stands for both red and blue, so blue should be 2=blue. The key only has the numbers 0 and 1. The number 3 has no colour, so the row should be 1 1 1.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add A colour key: whole numbers stand for colours to a class →

This module's key terms are also in a printable crossword (Modules 59–71) and word search (Modules 44–71).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning
Duo
What does a colour key do?
It locks a picture with a passwordIt matches each number to a colour
Matches
1 = red, 1 = blue, 2 = yellow
↓
The number 1 is used for two different colours, so nobody can tell if a 1 is red or blue. Each number needs its own colour.
Applying
Meanings
Term
colour key
Meaning
A list that matches each whole number to a colour, like 1 = red, 2 = blue and 3 = yellow, so a grid of numbers can show a picture.
Practice
Colour key
Testing
Gaps
row: 1 2 # red, yellow, blue
Check Answer
Spots
1Key: 0=white 1=red 1=blue
2Row 1: 0 1 0

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

The 'Oryx' badge — Desert Navigator, one of Cloodit's 106 collectible badges
Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy
Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games
Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print
Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. What does a colour key do?
A. It locks a picture with a password
B. It matches each number to a colour ✓
A colour key is a list that says which number stands for which colour, like 1 = red.
2. The key says 1 = red, 2 = blue, 3 = yellow. What colour does a 2 in the grid show?
A. Yellow
B. Blue ✓
Look up 2 in the key: 2 = blue.
3. Which key is a good way to set up a colour key for three colours?
A. 1 = red, 2 = blue, 3 = yellow ✓
B. 1 = red, 1 = blue, 1 = yellow
Each colour needs its own number. If three colours share the number 1, we can't tell them apart.
4. A picture uses 0 for the background. What does that mean?
A. Every 0 in the grid is the background colour ✓
B. Every 0 in the grid is a hole with nothing in it
0 is a number like any other. In the key we choose 0 to mean the background colour, such as white.
5. Halfway through a picture, you can change the key so 1 means green instead of red.
A. False ✓
B. True
Keep the same key for the whole picture. If the key changes, the numbers give the wrong colours.

Match the Pairs

1 = red, 2 = blue, 3 = yellow → A colour key that matches each whole number to one colour
0 = white → The background colour is given the number 0 in the key
A key lets a number stand for a colour, so a grid of numbers can show a picture → Row 1: 1 2 2 1 (1 = red, 2 = blue)
The same key must be used for the whole picture so each number always means the same colour → 3 = yellow in every row of the grid
1 = red, 1 = blue, 2 = yellow → The number 1 is used for two different colours, so nobody can tell if a 1 is red or blue. Each number needs its own colour.
Row 1 uses 1 = red, Row 2 uses 1 = green → The key changes between rows. The key must stay the same for the whole picture so 1 always means the same colour.

Key Term

colour key
A list that matches each whole number to a colour, like 1 = red, 2 = blue and 3 = yellow, so a grid of numbers can show a picture.

Fill in the Blanks

1. key: 1 = red, 2 = blue, 3 = yellow row: 1 3 2 # red, yellow, blue
Hint: Type the whole number the key gives to yellow, so the row matches its colour comment.
2. key: 0 = white, 1 = red, 2 = blue row: 0 1 1 0 # white, red, red, white
Hint: Type the number used for the background colour in this key.
3. key: 1 = red, 2 = blue row1: 1 2 2 # red, blue, blue row2: 1 2 1 # red, blue, red
Hint: Use the same key as row 1 and type the number that stands for blue.
4. key: 0 = white, 1 = red, 2 = blue row: 1 2 0 # red, blue, white
Hint: Type the colour word that matches number 1, using the row comment to work it out.
5. key: 0 = white, 1 = red, 2 = blue row: 2 0 1 colours: blue, white, red
Hint: Decode the last number in the row by looking it up in the key and type its colour.

Spot the Error

Question 1
A Key: 0=white 1=red 1=blue
B Row 1: 0 1 0
C Row 2: 1 2 1
D Row 3: 0 1 0
Line A — Each colour needs its own number. In this key 1 stands for both red and blue, so blue should be 2=blue.
Question 2
A Key: 0=white 1=red
B Row 1: 0 1 0
C Row 2: 1 3 1
D Row 3: 0 1 0
Line C — The key only has the numbers 0 and 1. The number 3 has no colour, so the row should be 1 1 1.
Question 3
A Key: 0=white 1=green 2
B Row 1: 0 2 0
C Row 2: 2 1 2
D Row 3: 0 2 0
Line A — The key has to match every number to a colour. The number 2 has no colour here, so it should say 2=blue.
Question 4
A 0 = white
B 1 = red
C 2 = blue
D Row 1: red 2 1
E Row 2: 0 1 0
Line D — A picture grid is written with numbers, and the key turns them into colours. Row 1 should be 1 2 1, not the word red.
Question 5
A 0 = white (background)
B 0 = blue
C Row 1: 0 1 0
D Row 2: 1 1 1
Line B — The number 0 is already the white background. Giving 0 a second colour confuses the key. Blue should be 1 = blue.

Student with a class code? Join your class →