tkColorChooser

from Tkinter import*

import tkColorChooser #Libreria para obtener la gama de colores

v0=Tk()

v0.title('Ventana principal')

v0.config(bg='green')

v0.geometry("500x500")

def mostrar(num):

    a=tkColorChooser.askcolor()

    v1=Toplevel(v0)

    v1.title('ventana hija')

    v1.protocol('wn_DELETE_WINDOW', "onexit")

    v1.geometry("300x300")

    if num == 1:

        canvas1=Canvas(v1, width=200,height=200,bg='white')

        canvas1.pack(expand=YES, fill=BOTH)

        canvas1.create_line(10,200,200,10, width=10, fill=(a[1]))

        print a

    elif num==2:

        canvas2 = Canvas(v1, width=200, height=200, bg='white')

        canvas2.pack(expand=YES, fill=BOTH)

        canvas2.create_rectangle(10, 200, 200, 10, width=10, fill=(a[1]))

        print a

    elif num==3:

        canvas3 = Canvas(v1, width=200, height=200, bg='white')

        canvas3.pack(expand=YES, fill=BOTH)

        canvas3.create_oval(20, 200, 200, 20, width=10, fill=(a[1]))

        print a

def ocultar(ventana): ventana.destroy()

def ejecutar(f):v0.after(200,f)

b1=Button(v0, text='Abrir ventana con linea', command=lambda:ejecutar(mostrar(1)))

b1.grid(row=1,column=1)

b2=Button(v0, text='Abrir ventana con cuadro', command=lambda:ejecutar(mostrar(2)))

b2.grid(row=1,column=2)

b3=Button(v0, text='Hacer ovalo', command=lambda:ejecutar(mostrar(3)))

b3.grid(row=1,column=3)

v0.mainloop()

tkColoChooser nos permite seleccionar el color deseado