RGB LED color mixing in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this RGB LED color mixing code?

Consider this Python code controlling an RGB LED on a Raspberry Pi. What color will the LED show?

Raspberry Pi

red = 255
green = 100
blue = 0

if red > green and red > blue:
    color = 'Red'
elif green > red and green > blue:
    color = 'Green'
else:
    color = 'Blue'

print(color)

A Red

B Green

C No color

D Blue

💡 Hint

Check which color value is the highest number.

The red value (255) is greater than green (100) and blue (0), so the output is 'Red'.

❓ Predict Output

intermediate

What is the combined color output for these RGB values?

This code mixes RGB values to create a color. What is the printed output?

Raspberry Pi

def mix_color(r, g, b):
    return f'#{r:02X}{g:02X}{b:02X}'

color_code = mix_color(0, 128, 128)
print(color_code)

A #808000

B #800080

C #008080

D #000000

💡 Hint

Look at the hexadecimal format for green and blue values.

The green and blue values are both 128 decimal, which is 80 in hex, so the combined hex color is '#008080'.

🔧 Debug

advanced

Why does this RGB LED code cause an error?

Find the error in this Raspberry Pi RGB LED control code and identify the error type.

Raspberry Pi

red = 255
green = 255
blue = 255

color = {red, green, blue}
print(color)

A NameError

B SyntaxError

C TypeError

D It prints a set of values

💡 Hint

Look at the curly braces and what they create in Python.

Curly braces with comma-separated values create a set {255, 255, 255}, so the code prints the set.

❓ Predict Output

advanced

What is the output of this PWM brightness adjustment code?

This code adjusts brightness of an RGB LED using PWM values. What is printed?

Raspberry Pi

brightness = 0.5
red = int(255 * brightness)
green = int(100 * brightness)
blue = int(50 * brightness)

print(red, green, blue)

A 127 50 25

B 128 50 25

C 127 49 25

D 128 49 25

💡 Hint

Remember int() truncates decimals down.

255*0.5=127.5 truncated to 127, 100*0.5=50, 50*0.5=25, so output is '127 50 25'.

🧠 Conceptual

expert

Which option correctly describes additive color mixing for RGB LEDs?

When mixing colors with RGB LEDs, which statement is true?

A Adding green and blue light produces red light.

B Adding red and green light produces yellow light.

C Adding red and green light produces cyan light.

D Adding red and blue light produces green light.

💡 Hint

Think about how light colors combine, not paint.

In additive color mixing, red plus green light makes yellow light.