以这个模板，写代码，画出七色蛇

from turtle import *

# if you want to change color, just change this
colors = ["red", "yellow", "blue", "orange", "black", "green", "purple"]

setup(650, 350, 200, 200)
penup()
fd(-250)
pendown()
pensize(25)
c = 0
seth(-40)


for i in range(4):
    pencolor(colors[c])
    c += 1
    circle(40, 80)
    circle(-40, 80)

pencolor(colors[c])
c += 1
circle(40, 80 / 2)
fd(40)
pencolor(colors[c])
c += 1
circle(16, 180)
pencolor(colors[c])
fd(40 * 2 / 3)

增加一个color list，for 循环的时候调用pencolor就好了