← ACARA Digital Technologies Years 7–8

Reading RGB values for common colours

Pure red: red at full 255, green and blue at 0. Green is (0, 255, 0), blue is (0, 0, 255), and mixing red and green light makes yellow (255, 255, 0).

Part of: ACARA Digital Technologies Years 7–8 — Representing Text, Images and Sound — Module 34

Understanding Reading RGB values for common colours in ACARA Digital Technologies Years 7–8

What it does: Red is the first number, so 255 first and 0 for green and blue makes pure red. Blue is the third number, so turning only the blue slider up to 255 gives rgb(0, 0, 255). Screens mix light, so red and green at full strength make yellow. Purple needs red and blue. Red is the first slider. Full red with the other two at 0 gives (255, 0, 0), which is pure red. The first number controls red, so full red needs 255 first, not last.

Common mistakes: Yellow is red and green at full with no blue: rgb(255, 255, 0). Setting blue to 255 as well makes white. Yellow needs red and green both at 255. With green at 0 the mixer shows pure red, so line 2 should set green to 255.

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 Reading RGB values for common colours to a class →

This module's key terms are also in a printable crossword (Modules 128–152) and word search (Modules 69–152).

Take this worksheet further — free with Cloodit

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

Learning
Duo
Which RGB value gives pure red?
(0, 0, 255)(255, 0, 0)
Matches
rgb(0, 0, 255) for pure red
↓
The 255 is in the blue position. Red is the first number, so pure red is rgb(255, 0, 0).
Applying
Meanings
Term
rgb(255, 0, 0)
Meaning
Pure red: red at full 255, green and blue at 0. Green is (0, 255, 0), blue is (0, 0, 255), and mixing red and green light makes yellow (255, 255, 0).
Practice
<div style="background: rgb(255, 0, 0)">Red</div>
Testing
Gaps
colour = rgb(, 0, 0)
Check Answer
Spots
3blue = rgb(0, 0, 255)
4yellow = rgb(255, 255, 255)

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

The 'Ostrich' badge — Full Sprint, 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. Which RGB value gives pure red?
A. (0, 0, 255)
B. (255, 0, 0) ✓
Pure red uses red at full strength (255) with green and blue switched off (0). (0, 0, 255) is pure blue.
2. Which RGB value gives pure green?
A. (0, 255, 0) ✓
B. (255, 0, 0)
Green is the middle number in (R, G, B). Setting it to 255 and the others to 0 gives pure green.
3. True or false: (0, 0, 255) is pure blue.
A. True ✓
B. False
The blue value is the last number. At 255 with red and green at 0, you get pure blue.
4. What colour do you get by mixing red and green light at full strength: (255, 255, 0)?
A. Purple
B. Yellow ✓
Screens mix light, so red and green at full strength make yellow. Purple needs red and blue.
5. Which are the three primary colours of light used in RGB?
A. Red, green and blue ✓
B. Red, yellow and blue
RGB stands for Red, Green, Blue. Red, yellow and blue are the primary colours for paint, not light.

Match the Pairs

rgb(0, 255, 0) → Pure green: only the green light is on at full strength, red and blue are off.
rgb(255, 255, 0) → Yellow: red and green light are both at full strength and blue is off.
Pure red has red at full strength and green and blue switched off. → rgb(255, 0, 0)
Pure blue has only the blue slider turned all the way up to 255. → rgb(0, 0, 255)
rgb(0, 0, 255) for pure red → The 255 is in the blue position. Red is the first number, so pure red is rgb(255, 0, 0).
rgb(255, 0, 255) for yellow → Yellow needs red and green on, not blue. It should be rgb(255, 255, 0).

Key Term

rgb(255, 0, 0)
Pure red: red at full 255, green and blue at 0. Green is (0, 255, 0), blue is (0, 0, 255), and mixing red and green light makes yellow (255, 255, 0).

Fill in the Blanks

1. # Pure red colour = rgb(255, 0, 0)
Hint: Type the value for the red channel at its maximum brightness.
2. # Pure green colour = rgb(0, 255, 0)
Hint: Type the value for the green channel at its maximum brightness.
3. # Pure blue colour = rgb(0, 0, 255)
Hint: Type the value for the blue channel at its maximum brightness.
4. # Red + green light makes yellow colour = rgb(255, 255, 0)
Hint: Yellow uses no blue light, so type the blue channel value.
5. # Yellow colour = rgb(255, 255, 0)
Hint: Type the name of the function that sets red, green and blue light levels.

Spot the Error

Question 1
A red = rgb(255, 0, 0)
B green = rgb(0, 255, 0)
C blue = rgb(0, 0, 255)
D yellow = rgb(255, 255, 255)
Line D — Yellow is red and green at full with no blue: rgb(255, 255, 0). Setting blue to 255 as well makes white.
Question 2
A set red slider to 255
B set green slider to 0
C set blue slider to 0
D colour is yellow
Line B — Yellow needs red and green both at 255. With green at 0 the mixer shows pure red, so line 2 should set green to 255.
Question 3
A red = 0
B green = 255
C blue = 255
D colour = rgb(red, green, blue)
E show(colour) # pure green
Line C — Pure green is (0, 255, 0), so blue must be 0. With blue at 255 the colour would be cyan.
Question 4
A blue = rgb(255, 0, 0)
B red = rgb(255, 0, 0)
C green = rgb(0, 255, 0)
Line A — rgb(255, 0, 0) is pure red. Pure blue has red and green at 0 and blue at 255: rgb(0, 0, 255).
Question 5
A light1 = rgb(255, 0, 0)
B light2 = rgb(0, 255, 0)
C mixed = light1 + light2
D result = rgb(0, 255, 255)
E print(result) # yellow
Line D — Mixing red light (255, 0, 0) with green light (0, 255, 0) gives (255, 255, 0), which is yellow. (0, 255, 255) is cyan.

Student with a class code? Join your class →