sketch3.py

from tkinter import *
from tkinter import ttk

lastx, lasty = 0, 0
color = "black"

def xy(event):
    global lastx, lasty
    lastx, lasty = event.x, event.y

def setColor(newcolor):
    global color
    color = newcolor
    canvas.dtag('all', 'paletteSelected')
    canvas.itemconfigure('palette', outline='white')
    canvas.addtag('paletteSelected', 'withtag', 'palette%s' % color)
    canvas.itemconfigure('paletteSelected', outline='#999999')

def addLine(event):
    global lastx, lasty
    canvas.create_line((lastx, lasty, event.x, event.y), fill=color, width=5, tags='currentline')
    lastx, lasty = event.x, event.y

def doneStroke(event):
    canvas.itemconfigure('currentline', width=1)        

root = Tk()
root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=1)

canvas = Canvas(root)
canvas.grid(column=0, row=0, sticky=(N, W, E, S))
canvas.bind("<Button-1>", xy)
canvas.bind("<B1-Motion>", addLine)
canvas.bind("<B1-ButtonRelease>", doneStroke)

id = canvas.create_rectangle((10, 10, 30, 30), fill="red", tags=('palette', 'palettered'))
canvas.tag_bind(id, "<Button-1>", lambda x: setColor("red"))
id = canvas.create_rectangle((10, 35, 30, 55), fill="blue", tags=('palette', 'paletteblue'))
canvas.tag_bind(id, "<Button-1>", lambda x: setColor("blue"))
id = canvas.create_rectangle((10, 60, 30, 80), fill="black", tags=('palette', 'paletteblack', 'paletteSelected'))
canvas.tag_bind(id, "<Button-1>", lambda x: setColor("black"))	

root.mainloop()