How Can I get the Event Source where I Click ContextMenu

Below you'll find my basic WPF / C# code to create and show a Context Menu. I currently got a problem I want you help me.

//Create Context Menu
            MenuItem mColorBlack = new MenuItem();
            mColorBlack.Header = "Black";
            mColorBlack.Click += onClickedContextMenuItem;
            MenuItem mColorRed = new MenuItem();
            mColorRed.Header = "Red";
            mColorRed.Click += onClickedContextMenuItem;
            MenuItem mColorBlue = new MenuItem();
            mColorBlue.Header = "Blue";
            mColorBlue.Click += onClickedContextMenuItem;
            MenuItem mColorGreen = new MenuItem();
            mColorGreen.Header = "Green";
            mColorGreen.Click += onClickedContextMenuItem;

            ContextMenu contextmenu = new ContextMenu();
            contextmenu.Items.Add(mColorBlack);
            contextmenu.Items.Add(mColorRed);
            contextmenu.Items.Add(mColorBlue);
            contextmenu.Items.Add(mColorGreen);


                  //Create TextBox
                  TextBox textBox1= new TextBox();
            textBox1.Text = "New TextBox";
            textBox1.AcceptsReturn = true;
            textBox1.TextWrapping = TextWrapping.Wrap;
            TextMenu contextMenu = new TextMenu();
            textBox1.ContextMenu = contextMenu;

//Create TextBox
                  TextBox textBox1= new TextBox();
            textBox1.Text = "New TextBox";
            textBox1.AcceptsReturn = true;
            textBox1.TextWrapping = TextWrapping.Wrap;
            TextMenu contextMenu = new TextMenu();
            textBox1.ContextMenu = contextMenu;

TextBox textBox2= new TextBox();
            textBox2.Text = "New TextBox";
            textBox2.AcceptsReturn = true;
            textBox2.TextWrapping = TextWrapping.Wrap;
            TextMenu contextMenu = new TextMenu();
            textBox2.ContextMenu = contextMenu;


              //ContextMenu Event Handler
        /// <summary>
        ///onClickedContextMenuItem
        /// </summary>
        private void onClickedContextMenuItem(object sender, RoutedEventArgs e)
        {
            //          
        }



WhatI want to do is  when I  chosse the text in the textbox,and right click in the textbox, then Chose a contextmenu item to change color for the selected words;
it will do the onClickedContextMenuItem funtion.
Now I want to Know in onClickedContextMenuItem funtion,How Can I get  the menuItem Name that I clicked.
And which textbox  should be change?

Please help me.