Markers, Line Styles & Colors

Reviewed & published by Brayan K

Matplotlib is a Python library for creating charts and visualizations — and this lesson is about styling them, so each line looks exactly the way you want.

Part of the free Matplotlib course at LearnCodingFast — hands-on lessons with worked examples and the output they print, plus practice exercises and a quick quiz.

You'll set colors, switch between solid, dashed, and dotted lines, add point markers, and learn the compact format-string shortcut like 'ro--'.

What You'll Learn in This Lesson

• Setting a line color with color=
• Choosing a line style with linestyle=
• Controlling thickness with linewidth=
• Adding point markers with marker=
• Sizing markers with markersize=
• The shorthand format string like 'ro--'

1 Colors, Styles, and Width

Three keyword arguments give you full control of a line's appearance: color, linestyle, and linewidth.

• color="red" — name, letter ('r'), or hex ('#1f77b4')
• linestyle="--" — solid '-', dashed '--', dotted ':', dash-dot '-.'
• linewidth=2.5 — thickness in points

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5, 6]
y = [10, 14, 12, 18, 22, 20]

# A thick, dashed, green line
plt.plot(x, y, color="green", linestyle="--", linewidth=3)

plt.show()

What you'll see: a single line that is clearly green, drawn as a series of dashes rather than a solid stroke, and noticeably thicker than the default.

2 Markers on the Data Points

Markers draw a shape at each data point, which is useful when you want to highlight the exact values, not just the trend. Use marker= and size them with markersize=.

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [3, 8, 5, 12, 9]

# Blue line with large circle markers at each point
plt.plot(x, y, color="blue", marker="o", markersize=10)

plt.show()

What you'll see: a blue line with a bold filled circle sitting on every data point, making each of the five measured values easy to spot.

3 The Shorthand Format String

Matplotlib accepts a compact third argument that bundles color, marker, and line style into one string. 'ro--' means red circles joined by a dashed line. The order is color, then marker, then style.

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [2, 5, 3, 8, 6]

# 'ro--' = red color, circle markers, dashed line
plt.plot(x, y, "ro--")

# 'g^-' = green, triangle markers, solid line
y2 = [1, 3, 2, 5, 4]
plt.plot(x, y2, "g^-")

plt.show()

What you'll see: a red dashed line with circle markers and a green solid line with triangle markers, both fully styled from a single short string each.

🎯 Your Turn: Fill in the Blanks

Replace each ___ to style this line your way.

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [4, 9, 7, 14, 11]

plt.plot(
    x, y,
    color="___",        # try "purple"
    linestyle="___",    # try "--" for dashed
    marker="o",
    markersize=___      # try 8
)

plt.show()

📋 Common Errors & Quick Reference

❌ ValueError: Unrecognized character / invalid format string

Your format string uses letters Matplotlib doesn't know. Stick to valid color, marker, and style codes like 'ro--'.

❌ My markers don't appear

You set linestyle but no marker. Add marker="o" to show points.

🏆 Mini Challenge: Two Styled Lines

Plot two lines with contrasting colors, styles, and markers.

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5, 6]
plan = [10, 20, 30, 40, 50, 60]
actual = [8, 19, 27, 35, 48, 55]

# 1. Plan: blue dashed line with square markers
plt.plot(x, plan, color="blue", linestyle="--", marker="s", label="Plan")

# 2. Actual: red solid line with circle markers
plt.plot(x, actual, color="red", linestyle="-", marker="o", label="Actual")

plt.legend()
plt.show()

import matplotlib.pyplot as plt
from matplotlib.colors import to_hex

fig, ax = plt.subplots()
ax.plot([1, 2, 3], [1, 3, 2], color="#d62728", linewidth=3, linestyle=":", marker="s", markersize=8, alpha=0.8)

line = ax.lines[0]
print("Colour:     ", to_hex(line.get_color()))
print("Width:      ", line.get_linewidth())
print("Style:      ", line.get_linestyle())
print("Marker:     ", line.get_marker())
print("Marker size:", line.get_markersize())
print("Alpha:      ", line.get_alpha())

# ✅ Expected output:
# Colour:      #d62728
# Width:       3.0
# Style:       :
# Marker:      s
# Marker size: 8.0
# Alpha:       0.8

❓ Frequently Asked Questions

Lesson complete — you control the look!

You set colors, line styles, widths, and markers, and learned the compact format-string shortcut.

Practice quiz

Continue this course

• Previous: Labels, Titles & Legends
• Next: Saving Figures — Export charts to PNG, SVG, and PDF with savefig and the right DPI
• Quick reference: Matplotlib cheat sheet › Styling

Frequently asked questions

How do I change a line's color?

Pass color= to plt.plot(), such as color='red' or a hex code like color='#1f77b4'. You can use named colors, single-letter codes like 'r' and 'g', or hex strings.

How do I make a dashed line?

Use the linestyle argument: linestyle='--' for dashed, ':' for dotted, '-.' for dash-dot, and '-' (the default) for solid.

What is the shorthand format string?

It is a compact third positional argument that combines color, marker, and line style, like 'ro--' meaning red circles joined by a dashed line. The order is color, marker, then line style.

How do I add point markers?

Pass marker='o' for circles, 's' for squares, '^' for triangles, and so on. Control their size with markersize, for example marker='o', markersize=8.