import pygame
import sys

FPS = 60
W = 300
H = 500
WHITE = (255, 255, 255)
GREEN = (0,100, 0)
RED = (100, 0, 0)
YELLOW = (200,200,0)
sc = pygame.display.set_mode((W, H))
clock = pygame.time.Clock()
pygame.time.set_timer(pygame.USEREVENT, 1000)
x = W // 2
y = H // 2
r = 50

counter = 0
while 1:
    for i in pygame.event.get():
        if i.type == pygame.QUIT:
            sys.exit()
        if i.type == pygame.USEREVENT:
         counter = counter + 1
         if counter == 4: counter = 1
         
    sc.fill(WHITE)
    
    if counter == 1:
     GREEN =(0,100,0)
     RED = (255, 0,0)
    if counter == 2:
     RED = (100, 0,0)
     YELLOW = (255,255,0)
    if counter == 3:
     YELLOW = (200,200,0)
     GREEN = (0,255, 0)

     
    pygame.draw.circle(sc, RED, (150, 50), r)
    pygame.draw.circle(sc, YELLOW, (150, 150), r)
    pygame.draw.circle(sc,GREEN, (150, 250), r)
    pygame.display.update()
    clock.tick(FPS)