what i did is this
i masked green yellow and brown thats the reason the fingers not turned into black
# find the green color
mask_green = cv2.inRange(hsv, (36,0,0), (86,255,255))
# find the brown color
mask_brown = cv2.inRange(hsv, (8, 60, 20), (30, 255, 200))
# find the yellow color in the leaf
mask_yellow = cv2.inRange(hsv, (21, 39, 64), (40, 255, 255))