For i in range(4): bob color(color[i%4])

import turtle

def kv(a):

for i in range(4):
bob.color(color[i%4])
bob.forward(a)
bob.left(90)
bob=turtle.Turtle()
bob.speed(100)
bob.width(3)
bob.color('red')
colors=['red', 'brown', 'green', 'blue']
uzunlik=20
for i in range(80):
bob.circle(uzunlik)
bob.right(10)
uzunlik+=3