This is code that I used to generate and post an award-winning piece of art on DeviantArt over a decade ago...

rationals.py

from tkinter import *
import time
root = Tk()
def n2color(n):
        p = 1.1
        def f(x):
                return p**-x
        color = ''
        for i in range(1):
                bit1 = hex(int(255*f(n)))[2:]
                bit2 = hex(int(255*(1-f(n))))[2:]
                if len(bit1) == 1:
                        bit1 = '0' + bit1
                if len(bit2) == 1:
                        bit2 = '0' + bit2
        color = '#' + '00' + bit1 + '00'
        return color
w = 2500
h = 2500
canvas1 = Canvas(root, width = w, height = h)
canvas1.pack()
n = 100.
k = 1.
while k <= n:
        print("k = " + str(int(k)), "color = " + n2color(k))
        dx = w/(4*k**1.5)
        dy = h/(4*k**1.5)
        for i in range(int(k) + 1):
                xc = (i/k)*w
                for j in range(int(k) + 1):
                        yc = (j/k)*h
                        canvas1.create_rectangle(xc - dx, yc - dy, xc + dx, yc + dy, fill = n2color(k), outline = n2color(k))
        k += 1
canvas1.update()
canvas1.postscript(file="rationals.ps", width=w, height=h)
root.mainloop()