To colorize the boxplot, you need to first use the patch_artist=True keyword to tell it that the boxes are patches and not just paths. Then you have two main options here:

1. set the color via ...props keyword argument, e.g.
   boxprops=dict(facecolor="red"). For all keyword arguments, refer to the documentation
2. Use the plt.setp(item, properties) functionality to set the properties of the boxes, whiskers, fliers, medians, caps.
3. obtain the individual items of the boxes from the returned dictionary and use item.set_<property>(...) on them individually. This option is detailed in an answer to the following question: python matplotlib filled boxplots, where it allows to change the color of the individual boxes separately.

The complete example, showing options 1 and 2:

import matplotlib.pyplot as plt
import numpy as np
data = np.random.normal(0.1, size=(100,6))
data[76:79,:] = np.ones((3,6))+0.2

plt.figure(figsize=(4,3))
# option 1, specify props dictionaries
c = "red"
plt.boxplot(data[:,:3], positions=[1,2,3], notch=True, patch_artist=True,
            boxprops=dict(facecolor=c, color=c),
            capprops=dict(color=c),
            whiskerprops=dict(color=c),
            flierprops=dict(color=c, markeredgecolor=c),
            medianprops=dict(color=c),
            )


# option 2, set all colors individually
c2 = "purple"
box1 = plt.boxplot(data[:,::-2]+1, positions=[1.5,2.5,3.5], notch=True, patch_artist=True)
for item in ['boxes', 'whiskers', 'fliers', 'medians', 'caps']:
        plt.setp(box1[item], color=c2)
plt.setp(box1["boxes"], facecolor=c2)
plt.setp(box1["fliers"], markeredgecolor=c2)
            

plt.xlim(0.5,4)
plt.xticks([1,2,3], [1,2,3])
plt.show()

You can change the color of a box plot using setp on the returned value from boxplot(). This example defines a box_plot() function that allows the edge and fill colors to be specified:

import matplotlib.pyplot as plt

def box_plot(data, edge_color, fill_color):
    bp = ax.boxplot(data, patch_artist=True)
    
    for element in ['boxes', 'whiskers', 'fliers', 'means', 'medians', 'caps']:
        plt.setp(bp[element], color=edge_color)

    for patch in bp['boxes']:
        patch.set(facecolor=fill_color)       
        
    return bp
    
example_data1 = [[1,2,0.8], [0.5,2,2], [3,2,1]]
example_data2 = [[5,3, 4], [6,4,3,8], [6,4,9]]

fig, ax = plt.subplots()
bp1 = box_plot(example_data1, 'red', 'tan')
bp2 = box_plot(example_data2, 'blue', 'cyan')
ax.legend([bp1["boxes"][0], bp2["boxes"][0]], ['Data 1', 'Data 2'])
ax.set_ylim(0, 10)
plt.show()

This would display as follows:

This question seems to be similar to that one (Face pattern for boxes in boxplots) I hope this code solves your problem

import matplotlib.pyplot as plt

# fake data
d0 = [[4.5, 5, 6, 4],[4.5, 5, 6, 4]]
d1 = [[1, 2, 3, 3.3],[1, 2, 3, 3.3]]

# basic plot
bp0 = plt.boxplot(d0, patch_artist=True)
bp1 = plt.boxplot(d1, patch_artist=True)

for box in bp0['boxes']:
    # change outline color
    box.set(color='red', linewidth=2)
    # change fill color
    box.set(facecolor = 'green' )
    # change hatch
    box.set(hatch = '/')

for box in bp1['boxes']:
    box.set(color='blue', linewidth=5)
    box.set(facecolor = 'red' )

plt.show()

Change the color of a boxplot

import numpy as np 
import matplotlib.pyplot as plt

#generate some random data
data = np.random.randn(200)
d= [data, data]
#plot
box = plt.boxplot(d, showfliers=False)
# change the color of its elements
for _, line_list in box.items():
    for line in line_list:
        line.set_color('r')

plt.show()