Design code

 

from turtle import*

import colorsys

speed(0)

h=0.2

bgcolor("black")

pensize(3)

for i in range(300):

    c=colorsys.hsv_to_rgb(h,1,1)

    color(c)

    h+=0.002

    fd(i)

    circle(20,70)

    if i%3==0:

        circle(20,70)

done()