title: Change colour in a row in Treeview
body: <p>In the following Python code I try to change the colour of rows in the Treeview table. It doesn't work. I try with tag.configure but... 
  As you can see what the function do is extract data from a sql database and put it in a Treeview table, depending line the colour should be different but it doesn't work... anu help?</p>
  
  <pre><code>from tkinter import *
  from tkinter import ttk
  import sqlite3
  
  root=Tk()
  
  FrameTabla=Frame(root)
  FrameTabla.pack()
  def mostrar_items():
  
  
      miConexion=sqlite3.connect("database")
      miCursor=miConexion.cursor()
  
  
      miCursor.execute("SELECT * FROM DATABASE ORDER BY USERID DESC")
  
      lista=miCursor.fetchall()
  
      for i in lista:
  
  
          if lista.index(i) % 2 == 0:
              Tabla.insert('', 0, text=i[0], values=(i[1], i[2]), tags=('par',))
  
  
          else: 
              Tabla.insert('', 0, text=i[0], values=(i[1], i[2]), tags=('impar',))
  
      miConexion.close()
  
  
  
  Tabla=ttk.Treeview(FrameTabla, heigh=20, columns=("Nombre", "Apellido"))
  Tabla.grid(row=0, column=0, columnspan=3)
  Tabla.tag_configure('par',background='white',foreground='black')
  Tabla.tag_configure('impar',background='black',foreground='white')
  Tabla.heading('#0', text = 'UserID', anchor = CENTER)
  Tabla.heading('Nombre', text = 'Nombre', anchor = CENTER)
  Tabla.heading('Apellido', text = 'Apellido', anchor = CENTER)
  Tabla.column('#0', width=120, anchor= CENTER)
  Tabla.column('Nombre', anchor = CENTER)
  Tabla.column('Apellido', anchor = CENTER)
  
  ScrollVert=Scrollbar(FrameTabla, command=Tabla.yview)
  ScrollVert.grid(row=0, column=4, sticky='nsew')
  
  mostrar_items()
  
  root.mainloop()
  </code></pre>