How to avoid line color repetition in matplotlib.pyplot?

When plotting multiple lines in matplotlib, the library automatically cycles through a default color sequence. To avoid line color repetition, you can manually specify unique colors using several approaches.

Method 1: Using Hexadecimal Color Codes

Specify unique hexadecimal color values for each line to ensure no repetition ?

import numpy as np
import matplotlib.pyplot as plt

# Set the figure size
plt.rcParams["figure.figsize"] = [10, 6]
plt.rcParams["figure.autolayout"] = True

# Create data points
x = np.linspace(0, 10, 100)

# Plot multiple lines with unique hex colors
plt.plot(x, np.sin(x), color="#FF5733", label="sin(x)", linewidth=2)
plt.plot(x, np.cos(x), color="#33A1FF", label="cos(x)", linewidth=2)
plt.plot(x, np.tan(x/2), color="#7D3C98", label="tan(x/2)", linewidth=2)
plt.plot(x, np.exp(-x/5), color="#2ECC71", label="exp(-x/5)", linewidth=2)

plt.legend()
plt.ylim(-2, 2)
plt.xlabel("X values")
plt.ylabel("Y values")
plt.title("Multiple Lines with Unique Colors")
plt.show()

Method 2: Using Named Colors

Matplotlib supports over 140 named colors that you can use directly ?

import numpy as np
import matplotlib.pyplot as plt

# Create data
x = np.linspace(0, 8, 100)

# Plot with named colors
plt.plot(x, x**0.5, color="crimson", label="sqrt(x)", linewidth=2)
plt.plot(x, x, color="forestgreen", label="x", linewidth=2)
plt.plot(x, x**1.5, color="royalblue", label="x^1.5", linewidth=2)
plt.plot(x, x**2, color="darkorange", label="x^2", linewidth=2)

plt.legend()
plt.xlabel("X values")
plt.ylabel("Y values")
plt.title("Named Colors Example")
plt.show()

Method 3: Using Color Palette

Generate a custom color palette to ensure unique colors for multiple lines ?

import numpy as np
import matplotlib.pyplot as plt

# Create data
x = np.linspace(0, 6, 100)
functions = [np.sin, np.cos, lambda x: np.sin(2*x), lambda x: np.cos(2*x), 
             lambda x: np.sin(x/2), lambda x: np.cos(x/2)]
labels = ["sin(x)", "cos(x)", "sin(2x)", "cos(2x)", "sin(x/2)", "cos(x/2)"]

# Custom color palette
colors = ['#FF6B6B', '#4ECDC4', '#45B7D1', '#96CEB4', '#FFEAA7', '#DDA0DD']

# Plot multiple functions with unique colors
plt.figure(figsize=(12, 8))
for i, (func, label, color) in enumerate(zip(functions, labels, colors)):
    plt.plot(x, func(x), color=color, label=label, linewidth=2)

plt.legend()
plt.xlabel("X values")
plt.ylabel("Y values")
plt.title("Multiple Functions with Color Palette")
plt.grid(True, alpha=0.3)
plt.show()

Comparison of Methods

Conclusion

Use hexadecimal codes for precise color control, named colors for simplicity, or color palettes for multiple lines. This ensures each line has a unique, visually distinct color in your matplotlib plots.