Specify the color

mv_dict = {'type': ['values', 'values'], 'quantity': [5, 10], 'category': ['mv', 'no_mv']}
df = pd.DataFrame(mv_dict)
alt.Chart(df).mark_bar().encode(
    y='type',
    x='sum(quantity)',
    color='category',
)

With this piece of code, the graph is generated automatically using blue for ‘mv’ and orange for ‘no_mv’

Since in some contexts, the color has an implicit connotation…could it be possible to specify what color I want to use for ‘mv’ (e.g. red) and what for ‘no_mv’ (e.g. green)?

[afonit]

Here you go:

import altair as alt
import pandas as pd
mv_dict = {'type': ['values', 'values'], 'quantity': [5, 10], 'category': ['mv', 'no_mv']}
df = pd.DataFrame(mv_dict)
alt.Chart(df).mark_bar().encode(
    y='type',
    x='sum(quantity)',
    color=alt.Color('category',
                   scale=alt.Scale(
            domain=['mv', 'no_mv'],
            range=['red', 'green'])))

[jakevdp]

You can also use alt.Color('category', scale=alt.Scale(scheme=scheme_name)) where scheme_name is a string that matches any of the available Vega color schemes: https://vega.github.io/vega/docs/schemes/#reference

Edit: scheme should be a scale argument