您可以执行以下操作将图例显示为修补：

import matplotlib
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches

colors = [['#01FF4F','#00FFff'],
           ['#FFEB00','#FFFF00']]
categories = ['A','B']
# categories and colors inside a dict
legend_dict=dict(zip(categories,colors))
# setting up lines for the plot and list for patches
patchList = []
fig, ax = plt.subplots()
# assigning each inner color for each categories to their respective plot lines and legend/patches
for key in legend_dict:
        data_key = mpatches.Patch(facecolor=legend_dict[key][0],
                                  edgecolor=legend_dict[key][1], label=key)
        ax.plot(np.random.randn(100).cumsum(), color=legend_dict[key][0], label=legend_dict[key][1])
        patchList.append(data_key)

ax.legend(handles=patchList, ncol=len(categories), fontsize='small')
plt.show()

输出：

在给出这个答案之前，我并不了解matplotlib，所以我不得不混合了两三个SO post才走到这一步（尝试/失败了一段时间）。

• https://stackoverflow.com/a/57791790/12349101
• https://stackoverflow.com/a/73832036/12349101（来自此帖子答案的一行）
• https://stackoverflow.com/a/39500357/12349101

既然您提到了Line 2d：

import matplotlib
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
from matplotlib.lines import Line2D

colors = [['#01FF4F','#00FFff'],
           ['#FFEB00','#FFFF00']]
categories = ['A','B']
# categories and colors inside a dict
legend_dict=dict(zip(categories,colors))
# setting up lines for the plot and list for patches
patchList = []
fig, ax = plt.subplots()
# assigning each inner color for each categories to their respective plot lines and legend/patches
for key in legend_dict:
        data_key = mpatches.Patch(facecolor=legend_dict[key][0],
                                  edgecolor=legend_dict[key][1], label=key)
        ax.plot(Line2D(np.random.randn(100).cumsum(), np.random.randn(100).cumsum()).get_data(), color=legend_dict[key][0], label=legend_dict[key][1])
        patchList.append(data_key)

ax.legend(handles=patchList, ncol=len(categories), fontsize='small')
plt.show()

输出：

一个耐人寻味的和补丁相关的帖子让我忍不住链接了起来：Make patches bigger used as legend inside matplotlib
最后，这里是一个关于在matplotlib上定制图例的不错的摘录：https://jakevdp.github.io/PythonDataScienceHandbook/04.06-customizing-legends.html

默认情况下显示此选项可能不起作用，因为线条和补丁之间存在太多差异。线条可以有线宽、标记、线条样式等。补丁可以有轮廓、阴影线等。
对于只有彩色的简单情况，可以使用矩形：

import matplotlib
import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
ax.plot(np.random.randn(100).cumsum(), color='tomato', label='red line')
ax.plot(np.random.randn(100).cumsum(), color='cornflowerblue', alpha=0.6, label='blue line')

handles, labels = ax.get_legend_handles_labels()
new_handles = [h if type(h) != matplotlib.lines.Line2D
               else plt.Rectangle((0, 0), 0, 0, lw=0, color=h.get_color(), alpha=h.get_alpha()) for h in handles]

ax.legend(new_handles, labels)
plt.show()