如何在pygame中用颜色填充我的图形？

import pygame

# 初始化pygame
pygame.init()

# 设置窗口尺寸
width, height = 800, 600
screen = pygame.display.set_mode((width, height))

# 设置颜色
red = (255, 0, 0)
green = (0, 255, 0)
blue = (0, 0, 255)

# 创建一个矩形
rect = pygame.Rect(100, 100, 200, 200)

# 填充矩形
pygame.draw.rect(screen, red, rect)

# 创建一个圆形
circle = pygame.draw.circle(screen, green, (400, 300), 100)

# 创建一个多边形
points = [(500, 100), (600, 200), (700, 100)]
polygon = pygame.draw.polygon(screen, blue, points)

# 刷新屏幕
pygame.display.flip()

# 游戏循环
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

# 退出pygame
pygame.quit()