2D pinball mask collisions?

Question

I am currently developing a 2d pinball game in python using the pygame library, I opted for the mask collision detection, here is a link to a post where it's well explained:

2D Collision detection for Pinball Game

I think I did everything but it's not working as wanted .

Here is my code for the physiscs of the ball:

from math import *
from Constants import *

def Getcolor(ballx,bally,screen,resources):
    screen.blit(resources["CollisionMain"], (220, 0))
    color=screen.get_at((ballx,bally))
    colore=color[1]
    return colore

def UpdateBall(ball,color):
    ballx=ball[1][0]
    bally=ball[1][1]
    lastpos = ball[1][0], ball[1][1]
    velocity=ball[2]
    if  -FRICTION_BALL <= velocity <= FRICTION_BALL :
        velocity = 0
    else:
        velocity += FRICTION_BALL if velocity < 0 else -FRICTION_BALL
    ball[2] = velocity
    ball[1][0] += velocity
    vectorx = sin(color / 255 * 2 * pi)
    vectory = cos(color / 255 * 2 * pi)
    if ballx+Ball_width<screen_width:
        ballx=screen_width-Ball_width
    if (bally+Ball_len)>screen_lenght:
        bally=screen_lenght-Ball_len
        #ball[1][1] -= 10
    else:
        if color == 255:
            ball[1][1] += Gravity
        else:
            ball[1][0],ball[1][1]=lastpos
            ball[1][0] += vectorx
            ball[1][1] += vectory

def DrawBall(screen,ball,resources):
    screen.blit(ball[0],(ball[1][0],ball[1][1]))

and here is my game engine code:

import pygame
import sys
from pygame.locals import *
from Constants import *
from ball import *

def Init():
    pygame.init()
    screen = pygame.display.set_mode((screen_width,screen_lenght))
    pygame.display.set_caption('Supinball')
    pygame.key.set_repeat(150,150)
    pygame.mixer.init(44100, -16, 2, 1024)
    return screen

def LoadResources():
    resources= dict()
    resources["MainLayer"] = pygame.image.load("resources/images/main_layer.png")
    resources["Ball"] = pygame.image.load("resources/images/Ball.png")
    resources["CollisionMain"] = pygame.image.load("resources/images/collision_main.png")
    resources["CollisionSpec"] = pygame.image.load("resources/images/collision_special.png")
    resources["Rflipper"] = pygame.image.load("resources/images/right_flipper.png")
    resources["Lflipper"] = pygame.image.load("resources/images/left_flipper.png")
    resources["Spring"] = pygame.image.load("resources/images/spring.png")
    resources["Music"] = pygame.mixer.Sound("resources/sounds/music.ogg")
    resources["Coin"] = pygame.mixer.Sound("resources/sounds/Coin.wav")
    resources["Hit"] = pygame.mixer.Sound("resources/sounds/hit.wav")
    resources["Tilted"] = pygame.mixer.Sound("resources/sounds/tilted.wav")
    resources["GameOver"] = pygame.mixer.Sound("resources/sounds/GameOver.ogg")
    resources["Font"] = pygame.font.Font('resources/Vdj.ttf', 30)
    return resources


def GameLoop(screen,resources):
    gameRunning = True
    ball = [resources["Ball"],[300,20],0]
    fpsClock = pygame.time.Clock()
    while gameRunning:
        ev = GetEvent(ball)
        gameRunning = ev[GAME_RUNNING]
        #resources["Music"].play(-1)
        color=Getcolor(int(ball[1][0]), int(ball[1][1]), screen, resources)
        print(color)
        UpdateBall(ball,color)
        #screen.blit(resources["MainLayer"], (0,0))
        DrawBall(screen,ball,resources)
        pygame.display.update()
        fpsClock.tick(FPS)

def GetEvent(ball):
    ev = [True,False,False,False,False,False,False,False,False,False]
    for event in pygame.event.get():
        if event.type == QUIT:
            ev[GAME_RUNNING] = False
        if event.type == MOUSEBUTTONUP:
            mousepos = pygame.mouse.get_pos()
            ball[1][0],ball[1][1]=mousepos
        if event.type == KEYDOWN:
            if event.key == K_DOWN:#compress spring
                ev[KEY_DOWN] = True
            if event.key == K_UP: #relax spring
                ev[KEY_UP] = True
            if event.key == K_LSHIFT: #left flipper
                ev[KEY_LSHIFT] = True
            if event.key == K_RSHIFT: #right flipper
                ev[KEY_RSHIFT] = True
        if event.type == KEYUP:
            if event.key == K_q: #insert coin
                ev[KEY_Q] = True
            if event.key == K_SPACE: #launch ball
                ev[KEY_SPACE] = True
            if event.key == K_LEFT:#tilt left
                ev[KEY_LEFT] = True
            if event.key == K_RIGHT:#tilt right
                ev[KEY_RIGHT] = True
            if event.key == K_p:#pause
                ev[KEY_P] = True
    return ev

def DestroyGame():
    pygame.quit()

and the constants code:

#screen
screen_lenght = 256
screen_width= 600
#fps
FPS=100
#events
GAME_RUNNING = 0
KEY_Q = 1
KEY_DOWN = 2
KEY_UP = 3
KEY_SPACE = 4
KEY_LSHIFT = 5
KEY_RSHIFT = 6
KEY_RIGHT = 7
KEY_LEFT = 8
KEY_P = 9
#ball physics
FRICTION_BALL=0.5
Gravity=1.9
Ball_width=11
Ball_len=9

But when I run it the ball is not colliding perfectly it's only colliding with the darkest spots and going through the light grey colors

If you look at this picture

the ball shouldn't be able to go through the bumpers but it does—I am sorry if my code is garbage, I am a beginner. :)

Here is a youtube link to a kinda working version of what I want to achieve:
https://www.youtube.com/watch?v=SXegewcVx8A