Altair在binding_radio中更改标签的颜色

import altair as alt
from vega_datasets import data

# 加载数据集
cars = data.cars()

# 创建单选框绑定对象
radio = alt.binding_radio(options=['Asia', 'Europe', 'USA'], name='Origin:')

# 创建选择器
selector = alt.selection_single(fields=['Origin'], bind=radio, init={'Origin': 'Asia'})

# 创建图表
chart = alt.Chart(cars).mark_circle().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
    color=alt.condition(selector, 'Origin:N', alt.value('lightgray'))
).add_selection(selector)

# 显示图表
chart