[python] 16進数表記のRGB値を暗くするメソッド

def darken(rgb, rate=0.5):
    rgb = rgb.replace('#', '')
    s = '#'
    for i in [0,2,4]:
        c = rgb[i:i+2]
        c = int(c, 16)
        c = int(c * rate)
        c = format(c, '02x')
        s += c
    return s

# 使用例
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
color_orig = [
    '#C5DAEE',
    '#ABCFE5',
    '#8DC0DD',
    '#6AADD5',
    '#4F9BCB',
    '#3787C0',
    '#2070B4',
    '#0F5BA3',
    '#08458B',
    '#08306B',
]
color = [
    [darken(c) for c in color_orig],
    color_orig,
]
df = pd.DataFrame([np.ones(10), np.ones(10)], columns=[x[1] + '\n' + x[0] for x in np.array(color).T])
df.T.plot.bar(color=color, stacked=True)
plt.legend().remove()
plt.yticks([])
plt.xticks(rotation=0)
plt.show()

out: