List box that uses data binding to populate the list box items.

   
  

<Canvas xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:src="clr-namespace:ListBoxEvent"  
    x:Class="ListBoxEvent.Pane1">
  <Canvas.Resources>
    <src:myColors x:Key="Colors"/>
  </Canvas.Resources>

    <StackPanel Margin="10, 10, 3, 3">
      <WrapPanel Width="500" Orientation="Horizontal" Name="rectanglesPanel">
        <WrapPanel.Resources>
          <Style TargetType="Rectangle">
            <Setter Property="Height" Value="20"/>
            <Setter Property="Width" Value="20"/>
            <Setter Property="Margin" Value="5"/>
          </Style>
        </WrapPanel.Resources>
      </WrapPanel>
      <ListBox Name="myListBox" HorizontalAlignment="Left" SelectionMode="Extended" 
            Width="265" Height="55" Background="HoneyDew" SelectionChanged="myListBox_SelectionChanged"
            ItemsSource="{Binding Source={StaticResource Colors}}" IsSynchronizedWithCurrentItem="true">
      </ListBox>
    </StackPanel>


</Canvas>
//File:Window.xaml.cs

using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Data;
using System.Windows.Media;
using System.Collections.ObjectModel;

namespace ListBoxEvent
{
    public class myColors : ObservableCollection<string>
    {
        public myColors()
        {
            Add("LightBlue");
            Add("Pink");
            Add("Red");
            Add("Purple");
            Add("Blue");
            Add("Green");
        }
    }
    public partial class Pane1 : Canvas
    {
        public Pane1() : base()
        {
            InitializeComponent();
        }
        void myListBox_SelectionChanged(object sender, SelectionChangedEventArgs args)
        {
            BrushConverter converter = new BrushConverter();
            foreach (string color in args.AddedItems)
            {
                if (GetRectangle(color) == null)
                {
                    Rectangle aRect = new Rectangle();
                    aRect.Fill = (Brush) converter.ConvertFrom(color);
                    aRect.Tag = color;
                    rectanglesPanel.Children.Add(aRect);
                }

            }
            foreach (string color in args.RemovedItems)
            {
                FrameworkElement removedItem = GetRectangle(color);
                if (removedItem != null)
                {
                    rectanglesPanel.Children.Remove(removedItem);
                }
            }
        }

        FrameworkElement GetRectangle(string color)
        {
            foreach (FrameworkElement rect in rectanglesPanel.Children)
            {
                if (rect.Tag.ToString() == color)
                    return rect;
            }

            return null;
        }

    }

}