在熊猫中，如何基于MultiIndex选择图中的曲线颜色？

Question

我有一个像这样的MultiIndex数据框

             Freights            Passengers
Station      Hogwarts              Hogwarts
Direction  Northbound Southbound Northbound Southbound
Date
2020-04-10          0          1          0          9
2020-04-11          0          2          0          8
2020-04-12          5          3         15         17
2020-04-13          6          4          4         26

我想获得一个带有每列曲线的图，Freights列应为红色，而Passengers列应为蓝色。

我设法按照下面的代码片段获得了结果，但是我想知道是否还有一种更惯用的方式（例如，避免for循环）。

import pandas as pd
import matplotlib.pyplot as plt

df = pd.DataFrame({'Date': ['2020-04-10', '2020-04-11', '2020-04-12', '2020-04-13','2020-04-10', '2020-04-11', '2020-04-12', '2020-04-13'],
'Station': ['Hogwarts', 'Hogwarts', 'Hogwarts', 'Hogwarts','Hogwarts', 'Hogwarts', 'Hogwarts', 'Hogwarts'],
'Direction': ['Southbound', 'Southbound', 'Southbound', 'Southbound','Northbound','Northbound','Northbound','Northbound'],
'Daily trains': [10,10,20,30,0,0,20,10],
'Freights': [1,2,3,4,0,0,5,6],
'Passengers': [9,8,17,26,0,0,15,4]})

df['Date'] = pd.to_datetime(df['Date'],format="%Y-%m-%d")

df1 = df.pivot_table(index='Date', columns=['Station','Direction'],values=['Freights','Passengers'])
colors = {'Freights':'red','Passengers':'blue'}

fig, ax = plt.subplots(1)
for i in df1:
    df1[i].plot(ax=ax,color=colors[i[0]])

ax.figure.savefig('so.png',bbox_inches='tight')