Unit 12.1A · Term 1

RGB Colors

Computers represent colors using the RGB model — three channels (Red, Green, Blue) each ranging from 0 to 255. Mixing these channels at different intensities creates over 16 million possible colors.

Learning Objectives

12.6.2.1 Determine standard colors by RGB code

Lesson Presentation

12.1A-rgb-colors.pdf · Slides for classroom use

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Conceptual Anchor

The Spotlight Analogy

Imagine three spotlights — Red, Green, Blue — shining on a white wall. Each has a dimmer (0 = off, 255 = full brightness). Overlap all at full = white. All off = black. Different combinations = different colors.

Rules & Theory

Standard RGB Colors

Color	RGB Code	Tuple in Python
Black	(0, 0, 0)	`(0, 0, 0)`
White	(255, 255, 255)	`(255, 255, 255)`
Red	(255, 0, 0)	`(255, 0, 0)`
Green	(0, 255, 0)	`(0, 255, 0)`
Blue	(0, 0, 255)	`(0, 0, 255)`
Yellow	(255, 255, 0)	`(255, 255, 0)`
Cyan	(0, 255, 255)	`(0, 255, 255)`
Magenta	(255, 0, 255)	`(255, 0, 255)`
Gray	(128, 128, 128)	`(128, 128, 128)`
Orange	(255, 165, 0)	`(255, 165, 0)`

Color Mixing Rules

Mix	Result	Why
Red + Green	Yellow	(255, 255, 0)
Red + Blue	Magenta	(255, 0, 255)
Green + Blue	Cyan	(0, 255, 255)
R + G + B (all max)	White	(255, 255, 255)
R + G + B (all zero)	Black	(0, 0, 0)
Equal R = G = B	Shade of gray	(128,128,128) = mid gray

Using RGB in Python

# Define colors as tuples
RED    = (255, 0, 0)
GREEN  = (0, 255, 0)
BLUE   = (0, 0, 255)
WHITE  = (255, 255, 255)
BLACK  = (0, 0, 0)
YELLOW = (255, 255, 0)
ORANGE = (255, 165, 0)

# Access individual channels
color = (100, 200, 50)
r = color[0]  # 100
g = color[1]  # 200
b = color[2]  # 50

# Total possible colors: 256 × 256 × 256 = 16,777,216

Hex Color Codes

RGB can also be written in hexadecimal: #FF0000 = Red, #00FF00 = Green, #0000FF = Blue. Each pair of hex digits = one channel (00–FF = 0–255).

Common Pitfalls

Additive vs Subtractive

RGB is additive (light-based): mixing all = white. This is the opposite of paint mixing (subtractive: mixing all = brown/black). Don't confuse the two!

Tasks

Remember

Write the RGB tuple for: red, green, blue, white, black, yellow.

Understand

What color does (0, 128, 128) produce? What about (255, 128, 0)?

Apply

Write a Python program that generates a random RGB color and prints its tuple.

Self-Check Quiz

Q1: What RGB tuple represents pure green?

(0, 255, 0) — only the green channel is at maximum.

Q2: What happens when R = G = B?

You get a shade of gray. (0,0,0) = black, (128,128,128) = gray, (255,255,255) = white.

Q3: How many total colors can RGB represent?

256 × 256 × 256 = 16,777,216 colors (over 16 million).