title: Detect if there is gray color in image by opencv Python
body: <p>I'm new to cv2 library and I want to make a program that will detect if there is gray color in an image at real time.
  Until now I took a code that will show me the screen in real time</p>
  <pre><code>import numpy as np
  import cv2
  import pyautogui
  from mss import mss
  from PIL import Image
  
  mon = {'top': 268, 'left': 968, 'width': 931, 'height': 599}
  
  sct = mss()
  
  while 1:
      sct.get_pixels(mon)
      img = Image.frombytes('RGB', (sct.width, sct.height), sct.image)
      cv2.imshow('test', np.array(img))
      if cv2.waitKey(25) &amp; 0xFF == ord('q'):
          cv2.destroyAllWindows()
          break
  </code></pre>
  <p>But I have no idea how to detect if gray color appear in the screen(The other questions is about if all the picture is gray and not if gray appear in the screen)</p>