Named colors and hex codes in Matplotlib

Introduction

Colors help make charts easy to understand and nice to look at. Using named colors or hex codes lets you pick exact colors for your plots.

You want to make a chart with specific colors to match a theme.

You need to highlight parts of a graph with clear, distinct colors.

You want to use colors that everyone can recognize by name.

You want to use custom colors by specifying their hex codes.

You want consistent colors across different charts or reports.

Syntax

Matplotlib

plt.plot(x, y, color='color_name')
plt.plot(x, y, color='#RRGGBB')

Use color='color_name' to pick a named color like 'red' or 'blue'.

Use color='#RRGGBB' to pick a color by its hex code, where RR, GG, BB are two-digit hex numbers.

Examples

This uses the named color 'green' for the line.

Matplotlib

plt.plot(x, y, color='green')

This uses a hex code for a bright orange color.

Matplotlib

plt.plot(x, y, color='#FF5733')

Scatter points colored with the named color 'navy'.

Matplotlib

plt.scatter(x, y, color='navy')

Sample Program

This code draws two lines: one red using a named color, and one blue using a hex code. It shows how to use both color types in matplotlib.

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4]
y1 = [10, 20, 25, 30]
y2 = [30, 23, 15, 10]

plt.plot(x, y1, color='red', label='Red line')
plt.plot(x, y2, color='#0000FF', label='Blue line')

plt.title('Example of Named Colors and Hex Codes')
plt.xlabel('X axis')
plt.ylabel('Y axis')
plt.legend()
plt.show()

Important Notes

Named colors are easy to remember but limited to common colors.

Hex codes give you millions of colors by mixing red, green, and blue.

You can find lists of named colors in matplotlib documentation or by running import matplotlib.colors as mcolors; print(mcolors.CSS4_COLORS).

Summary

Use named colors or hex codes to pick colors in matplotlib plots.

Named colors are simple words like 'red', 'blue', 'green'.

Hex codes start with '#' and use six hex digits to define colors.

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 '#'