Named colors and hex codes in Matplotlib - Mini Project: Build & Apply

Named colors and hex codes

📖 Scenario: You are creating a simple color chart to understand how named colors and hex codes work in plotting. This helps when you want to make your charts look nice and clear.

🎯 Goal: Build a small program that stores some named colors and their hex codes, then uses matplotlib to show these colors in a bar chart.

📋 What You'll Learn

Create a dictionary with color names as keys and their hex codes as values

Create a list of color names to use in the chart

Use matplotlib to plot a bar chart with bars colored by their hex codes

Print the dictionary of colors and hex codes

💡 Why This Matters

🌍 Real World

Knowing how to use named colors and hex codes helps you make charts and graphs that are easy to understand and visually appealing.

💼 Career

Data scientists and analysts often customize chart colors to match branding or to highlight important data points clearly.

1

Create a dictionary of colors and hex codes

Create a dictionary called colors with these exact entries: 'red': '#FF0000', 'green': '#00FF00', 'blue': '#0000FF', 'yellow': '#FFFF00', and 'purple': '#800080'.

Matplotlib

# Create the dictionary called colors with the given color names and hex codes
# Your code here

Hint

Use curly braces {} to create the dictionary. Each entry is a key-value pair separated by a colon.

2

Create a list of color names to plot

Create a list called color_names containing these exact strings in this order: 'red', 'green', 'blue', 'yellow', 'purple'.

Matplotlib

colors = {
    'red': '#FF0000',
    'green': '#00FF00',
    'blue': '#0000FF',
    'yellow': '#FFFF00',
    'purple': '#800080'
}
# Create the list called color_names with the given color names
# Your code here

Hint

Use square brackets [] to create the list with the color names as strings.

3

Plot a bar chart with colors using hex codes

Import matplotlib.pyplot as plt. Then create a bar chart with bars for each color in color_names. Use the hex codes from colors to set the bar colors. Use range(len(color_names)) for x positions and [1]*len(color_names) for bar heights. Set the bar colors with the color parameter using a list comprehension that gets hex codes from colors.

Matplotlib

colors = {
    'red': '#FF0000',
    'green': '#00FF00',
    'blue': '#0000FF',
    'yellow': '#FFFF00',
    'purple': '#800080'
}

color_names = ['red', 'green', 'blue', 'yellow', 'purple']

# Import matplotlib.pyplot as plt and create the bar chart with colored bars
# Your code here

Hint

Use plt.bar() with x positions as range(len(color_names)) and heights as a list of 1s. Use a list comprehension to get hex codes for colors.

4

Print the colors dictionary and show the plot

Print the colors dictionary. Then call plt.show() to display the bar chart.

Matplotlib

import matplotlib.pyplot as plt

colors = {
    'red': '#FF0000',
    'green': '#00FF00',
    'blue': '#0000FF',
    'yellow': '#FFFF00',
    'purple': '#800080'
}

color_names = ['red', 'green', 'blue', 'yellow', 'purple']

plt.bar(range(len(color_names)), [1]*len(color_names), color=[colors[name] for name in color_names])

# Print the colors dictionary and show the plot
# Your code here

Hint

Use print(colors) to show the dictionary. Use plt.show() to display the chart.

Practice

1. Which of the following is a valid named color in matplotlib?

easy

A. #12345G

B. bluish

C. red

D. 123456

Solution

1. Step 1: Understand named colors in matplotlib

   Matplotlib supports standard color names like 'red', 'blue', 'green', etc.

2. Step 2: Check each option

   red is 'red', a valid named color. #12345G has an invalid hex code with 'G'. bluish 'bluish' is not a recognized name. 123456 is just digits, not a named color.

3. Final Answer:

   red -> Option C

4. Quick Check:

   Named color 'red' is valid [OK]

Hint: Named colors are simple words like 'red' or 'blue' [OK]

Common Mistakes:

• Confusing invalid hex codes as named colors
• Assuming any color-like word is valid
• Using numbers without '#' as colors

2. Which of the following is the correct way to specify a hex color code in matplotlib?

easy

A. "#1a2b3c"

B. "1a2b3c"

C. "#12345"

D. "#xyz123"

Solution

1. Step 1: Recall hex color code format

   Hex codes start with '#' followed by exactly 6 hexadecimal digits (0-9, a-f).

2. Step 2: Validate each option

   "#1a2b3c" has '#' and 6 valid hex digits. "1a2b3c" misses '#'. "#12345" has only 5 digits. "#xyz123" contains invalid letters 'x' and 'z'.

3. Final Answer:

   "#1a2b3c" -> Option A

4. Quick Check:

   Hex code must start with '#' and have 6 hex digits [OK]

Hint: Hex codes start with '#' and have 6 hex digits [OK]

Common Mistakes:

• Omitting the '#' symbol
• Using wrong number of digits
• Including invalid characters

3. What color will the following matplotlib code produce?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], color="#00FF00")
plt.show()

medium

A. Black

B. Blue

C. Red

D. Green

Solution

1. Step 1: Understand the hex code used

   "#00FF00" is a hex code where red=00, green=FF, blue=00, meaning full green.

2. Step 2: Match hex code to color

   Since green is max and others zero, the line color will be bright green.

3. Final Answer:

   Green -> Option D

4. Quick Check:

   "#00FF00" means green color [OK]

Hint: Hex #00FF00 means full green, no red or blue [OK]

Common Mistakes:

• Confusing hex digits order
• Assuming #00FF00 is blue
• Ignoring case sensitivity in hex

4. Identify the error in this matplotlib color specification:

plt.plot([1, 2, 3], color="#123ABZ")

medium

A. Missing '#' in hex code

B. Invalid hex code due to 'Z'

C. Color name not recognized

D. Syntax error in plot function

Solution

1. Step 1: Check hex code characters

   Hex codes only allow digits 0-9 and letters A-F (case insensitive). 'Z' is invalid.

2. Step 2: Confirm error type

   The code has '#' and correct length, but 'Z' makes it invalid hex code.

3. Final Answer:

   Invalid hex code due to 'Z' -> Option B

4. Quick Check:

   Hex digits must be 0-9 or A-F only [OK]

Hint: Hex codes only use digits 0-9 and letters A-F [OK]

Common Mistakes:

• Ignoring invalid characters in hex
• Confusing missing '#' with invalid chars
• Assuming any letter is allowed in hex

5. You want to plot two lines in matplotlib: one red and one with a custom color #FF8800. Which code snippet correctly sets these colors?

hard

A. plt.plot(x, y1, color='red')
plt.plot(x, y2, color='#FF8800')

B. plt.plot(x, y1, color='#red')
plt.plot(x, y2, color='FF8800')

C. plt.plot(x, y1, color='ff8800')
plt.plot(x, y2, color='red')

D. plt.plot(x, y1, color='red')
plt.plot(x, y2, color='FF8800')

Solution

1. Step 1: Check named color usage

   Named colors like 'red' are used as strings without '#'. Adding '#' to named colors makes them invalid.

2. Step 2: Check hex code usage

   Hex codes must start with '#'. Omitting '#' for hex colors like 'FF8800' or using lowercase without '#' is invalid.

3. Final Answer:

   plt.plot(x, y1, color='red') plt.plot(x, y2, color='#FF8800') -> Option A

4. Quick Check:

   Named colors no '#', hex codes start with '#' [OK]

Hint: Named colors no '#'; hex codes start with '#' [OK]

Common Mistakes:

• Adding '#' to named colors
• Omitting '#' in hex codes
• Using lowercase hex without '#'