How can I select the right color to threshold an image with OpenCV?

Question

I'm trying to select the green color in an image using OpenCV (the method to do it comes from this website. The image I'm treating is :

Here is the code I tried to write.

import cv2
import matplotlib.pyplot as plt
import numpy as np

greenhsv = (60, 255, 255)
green2hsv=(70,100,170)
g_square = np.full((10, 10, 3), greenhsv, dtype=np.uint8)/255.0
plt.imshow(hsv_to_rgb(g_square))
plt.show()
g1_square = np.full((10, 10, 3), green2hsv, dtype=np.uint8)/255.0
plt.imshow(hsv_to_rgb(g1_square))
plt.show()

nucl = cv2.imread('./Pictures/image_nucleation_essai0.png')
nucl = cv2.cvtColor(nucl, cv2.COLOR_BGR2RGB)
plt.imshow(nucl)
plt.show()

hsv_nucl = cv2.cvtColor(nucl, cv2.COLOR_RGB2HSV)

mask = cv2.inRange(hsv_nucl, greenhsv,green2hsv)
result = cv2.bitwise_and(nucl, nucl, mask=mask)
plt.imshow(mask, cmap="gray")
plt.show()
plt.imshow(result)
plt.show()

The result is :

So the mask did not work.