How to change line color in Plotly

Plotly offers a wide range of options for customizing the appearance of your plots, including the color of lines. This is how to change line color in Plotly for various types of plots.

1. Changing Line Color in Scatter Plots

For scatter plots, you can control the line color using the line attribute within the trace.

import plotly.graph_objects as go

fig = go.Figure(data=[go.Scatter(x=[1, 2, 3], y=[4, 5, 6], mode='lines', line=dict(color='red'))])
fig.show()

This code creates a scatter plot with a red line. You can replace 'red' with any other color name (e.g., ‘blue’, ‘green’, ‘purple’), hexadecimal color code (e.g., ‘#FF0000’ for red), or RGB value (e.g., ‘rgb(255, 0, 0)’ for red).

You can also set the line color for multiple traces individually:

import plotly.graph_objects as go

fig = go.Figure()
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[4, 5, 6], mode='lines', line=dict(color='blue'), name="Line 1"))
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[7, 8, 9], mode='lines', line=dict(color='green'), name="Line 2"))
fig.show()

2. Changing Line Color in Line Plots

Line plots are essentially scatter plots with mode='lines'. Therefore, the same method applies:

import plotly.graph_objects as go

fig = go.Figure(data=[go.Line(x=[1, 2, 3], y=[4, 5, 6], line=dict(color='orange'))])
fig.show()

3. Changing Line Color in Bar Charts

For bar charts, you can change the color of the bar outlines (which look like lines) using the marker attribute:

import plotly.graph_objects as go

fig = go.Figure(data=[go.Bar(x=['A', 'B', 'C'], y=[10, 20, 15], marker=dict(line=dict(color='purple', width=2)))])
fig.show()

This code sets the outline color to purple and the width to 2.

4. Changing Line Color in Other Plot Types

Most Plotly chart types that involve lines (e.g., area charts, candlestick charts) use a similar approach. Look for the line attribute within the trace or the marker attribute (for outlines).

5. Setting Line Color Globally

You can set a default line color for all traces in your plot using the layout attribute:

import plotly.graph_objects as go

fig = go.Figure()
# ... add your traces ...

fig.update_layout(
    template="plotly_white",  # Optional: for a cleaner look
    scene=dict(
        xaxis=dict(
            linecolor="black"  # Set x-axis line color
        ),
        yaxis=dict(
            linecolor="black"  # Set y-axis line color
        )
    )
)
fig.show()

6. Color Scales

Plotly also supports color scales, which allow you to map data values to a range of colors. This is particularly useful for visualizing data with a continuous range. See the Plotly documentation for details on using color scales.

Examples of Color Values

• Color Names: ‘red’, ‘blue’, ‘green’, ‘black’, ‘white’, ‘gray’, ‘orange’, ‘purple’, etc.
• Hexadecimal Color Codes: ‘#FF0000’ (red), ‘#0000FF’ (blue), ‘#00FF00’ (green), etc.
• RGB Values: ‘rgb(255, 0, 0)’ (red), ‘rgb(0, 0, 255)’ (blue), ‘rgb(0, 255, 0)’ (green), etc.
• RGBA Values: ‘rgba(255, 0, 0, 0.5)’ (red with 50% opacity), etc.