# Just for variety...
import turtle as t

# Reminder: 
# Import everything FROM the library
# from turtle import *
# Import turtle library (as turtle)
# import turtle

t.pensize(4)
t.speed(0)
color_factor = 0
direction = 1
green_factor = .25
while True:    
    t.color((color_factor, green_factor, 1 - color_factor))
    t.circle(200)
    t.left(25)
    color_factor += 0.01 * direction
    green_factor += 0.005 * direction
    if color_factor >= 1:
        direction = -1
    if color_factor <= 0:
        direction = 1