The RGB colour model
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Which three colours of light does the RGB colour model mix to make screen colours?
2. How many numbers does the RGB model use to describe one colour?
3. Which one is a colour written in RGB form?
4. In the RGB colour (R, G, B), which number comes first?
5. On a screen, each pixel has its own RGB numbers.
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1(255, 0, 0) | AAn RGB colour with no red or green and full blue, so the pixel shows bright blue. | |
| 2(0, 0, 255) | BAn RGB colour with full red and no green or blue, so the pixel shows bright red. | |
| 3Every colour on a screen is a mix of red, green and blue light, so it needs three numbers in the order R, G, B. | CAn RGB colour needs three numbers, one each for red, green and blue. This one only has two, so the blue value is missing. | |
| 4Mixing full red and full green light, with no blue, makes yellow on a screen. | D(255, 255, 0) | |
| 5(255, 0) | EThe order is R, G, B, so the third number is blue, not red. (0, 0, 255) is blue. Red would be (255, 0, 0). | |
| 6(0, 0, 255) is red | F(R, G, B) |
C
Definitions
RGB
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
___(255, 0, 0)
2.
rgb(___, 0, 0)
3.
rgb(255, 255, _)
4.
color: rgb(___, 255, 255);
5.
let red = 255;
let _____ = 128;
let blue = 0;
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
# A pure green pixel
B
pixel = (0, 255)
C
print(pixel)
Question 2
A
# A pure blue pixel
B
pixel = (255, 0, 0)
C
print(pixel)
Question 3
A
pixel = (255, 0, 255)
B
# Red + green light is yellow
C
print(pixel)
Question 4
A
red = 255
B
green = 165
C
blue = 0
D
pixel = (red, blue, green)
E
print(pixel)
Question 5
A
h1 {
B
color: rgb(255, 0, 0);
C
background: rgb[0, 0, 0];
D
}
Answer Key
The RGB colour model
Section A: Quick Questions
Q1
B — Red, green and blue
Q2
A — Three: one each for red, green and blue
Q3
A — (255, 0, 0)
Q4
A — The amount of red
Q5
B — True
Section B: Match the Pairs
Q1
(255, 0, 0) → An RGB colour with full red and no green or blue, so the pixel shows bright red.
Q2
(0, 0, 255) → An RGB colour with no red or green and full blue, so the pixel shows bright blue.
Q3
Every colour on a screen is a mix of red, green and blue light, so it needs three numbers in the order R, G, B. → (R, G, B)
Q4
Mixing full red and full green light, with no blue, makes yellow on a screen. → (255, 255, 0)
Q5
(255, 0) → An RGB colour needs three numbers, one each for red, green and blue. This one only has two, so the blue value is missing.
Q6
(0, 0, 255) is red → The order is R, G, B, so the third number is blue, not red. (0, 0, 255) is blue. Red would be (255, 0, 0).
Section C: Definitions
Q1
RGB — A colour model where any screen colour is made by mixing red, green and blue light, written as three numbers (R, G, B). Each pixel on a screen uses its own three numbers.Section D: Fill in the Blanks
Q1
rgb(255, 0, 0)Q2
rgb(255, 0, 0)Q3
rgb(255, 255, 0)Q4
color: rgb(255, 255, 255);Q5
let red = 255;
let green = 128;
let blue = 0;Section E: Spot the Error
Q1
B — An RGB colour needs three numbers: red, green and blue. This pixel has only two. It should be (0, 255, 0).
Q2
B — RGB is written in the order (R, G, B). (255, 0, 0) is full red. Pure blue puts 255 in the third position: (0, 0, 255).
Q3
A — Yellow is made by mixing full red and full green light with no blue. That is (255, 255, 0). (255, 0, 255) is red plus blue, which gives magenta.
Q4
D — The order of an RGB colour is always red, green, blue. Swapping green and blue changes the colour. It should be (red, green, blue).
Q5
C — CSS writes the three RGB numbers inside round brackets, not square brackets. It should be rgb(0, 0, 0).