img = cv2.imread('img.bmp')
img_hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)
lower_red = np.array([0, 50, 50])
upper_red = np.array([10, 255, 255])
mask0 = cv2.inRange(img_hsv, lower_red, upper_red)
lower_red = np.array([170, 50, 50])
upper_red = np.array([180, 255, 255])
mask1 = cv2.inRange(img_hsv, lower_red, upper_red)
mask = mask0 + mask1
output_img = img.copy()
output_img[np.where(mask == 0)] = 0
output_hsv = img_hsv.copy()
output_hsv[np.where(mask == 0)] = 0
Finding red color using Python & OpenCV