How to Change the Black Line Color in Matplotlib Plots – A Quick Guide

1. Introduction

Hello everyone, I'm Pi Pi. Recently I asked a question in the Python “Most Powerful King” group about a mysterious black line that appears in a Matplotlib plot and how to change its color to gray.

2. Problem Description

The community asked: “What is this small black line? I want to set it to gray, but the information I found online about axis ticks does not match.”

3. Solution

Wu Chaojian provided the following code to customize the plot spines and axis colors:

import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(range(10))
ax.set_xlabel('X-axis')
ax.set_ylabel('Y-axis')
# ax.spines['bottom'].set_color('red')
ax.spines['top'].set_color('red')
ax.xaxis.label.set_color('red')
ax.tick_params(axis='x', colors='red')
plt.show()

The code successfully resolves the issue.

Yuliang also shared a comprehensive reference image showing various Matplotlib parameters for further customization.

4. Summary

This article demonstrates how to identify and modify the unwanted black line in a Matplotlib plot by adjusting spine and tick colors, providing a clear code example and additional resources for Python data‑visualization tasks.