I have a pandas dataframe of electricity generation mix. So it consists of electricity generation by different fuels. I want to assign a specific color to a specific fuel. In Matplotlib, it is convenient to assign a specific color to a specific category by passing a list of colors, e.g.

df.plot(kind="bar",color=["red","green","yellow"]

I wasn't able to assign color similarly for plots using Plotly. What would be the best way to assign specific color to specific categories in Plotly?

If you're aiming to assign a specific color to a specific fuel then color_discrete_sequence may work just fine for you as long as the structure of your dataset never changes. But the way to specify a color per category is best done through:

color_discrete_map = <dict>

And in your case:

fig = px.bar(df, color_discrete_map= {'Coal': 'black','Oil': 'grey','Gas': 'blue'})

This way you won't have to rely on the sequence of variables to match the sequence of your desired colors.

Example plot (with a different but structurally identical dataset)

Complete code

import plotly.express as px
import pandas as pd
df = px.data.stocks().set_index('date')
fig = px.bar(df, color_discrete_map= {'GOOG': 'black','AAPL': 'grey','AMZN': 'blue','FB': 'green','NFLX': 'red','MSFT':'firebrick'})
fig.show()

For other options please take a look at Plotly: How to define colors in a figure using plotly.graph_objects and plotly.express?? There you will find how to change the color sequence to whatever you want and still specify som exceptions through color_discrete_map.