import tkinter as tk

def select(event):
    widget = root.winfo_containing(event.x_root, event.y_root)
    if widget and hasattr(widget, 'selectable'):
        widget['bg'] = 'red'

root = tk.Tk()

for i in range(9):
    for e in range(9):
        b = tk.Button(root, text="X")
        b.selectable = True
        b.grid(row=e, column=i)

root.bind('<B1-Motion>', select)

l = tk.Label(root, text="Label which can't be selected")
l.grid(row=9, column=0, columnspan=9)
b = tk.Button(root, text="Button which can't be selected")
b.grid(row=10, column=0, columnspan=9)
e = tk.Entry(root)
e.insert('end', "Entry which can't be selected")
e.grid(row=11, column=0, columnspan=9)

root.mainloop()