Setting Triggers for a Custom Control in a Data Grid using WPF

I am new to WPF and am trying to achieve the following:

Display a DataGrid that has 'Round Buttons' as cells
Each button will have a different color based on its value
If 0 then button is  Black
If 1 then button is  Blue
If 2 then button is  Yellow
If 3 then button is  Pink

I've been able to get the DataGrid with the Round buttons
What I'm struggling to do is change the background color based on the value

Have inserted the project code below. Let me know if I have missed something or am doing it wrong

//////////////////////////////// XAML ////////////////////////////////////////////////////
<Window x:Class="ProgressGridTest.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:dg="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit"
    Title="Window1" Height="300" Width="300">
<Window.Resources>
 
    <Style x:Key="CustomRoundedButton" TargetType="Button" >
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Button}" >
                    <Border x:Name="bdr"
                            CornerRadius="36"   
                            Background="Red" 
                            BorderBrush="Red"  
                            BorderThickness="1"
                            Margin="6,0,6,0">
                        <ContentPresenter x:Name="cp"
                                          Content="{TemplateBinding Content}"
                                          HorizontalAlignment="Center" 
                                          VerticalAlignment="Center"/>                    
                    </Border>
                        <ControlTemplate.Triggers>                            
                            <Trigger SourceName="cp" Property="Content" Value="0">
                                <Setter TargetName="bdr" Property="Background" Value="Black"/>
                            </Trigger>
 
                            <Trigger SourceName="cp" Property="Content" Value="1">
                                <Setter TargetName="bdr" Property="Background" Value="Blue"/>
                            </Trigger>
 
                            <Trigger SourceName="cp" Property="Content" Value="2">
                                <Setter TargetName="bdr" Property="Background" Value="Yellow"/>
                            </Trigger>
 
                            <Trigger SourceName="cp" Property="Content" Value="3">
                                <Setter TargetName="bdr" Property="Background" Value="Pink"/>
                            </Trigger>                            
                        </ControlTemplate.Triggers>
 
                    </ControlTemplate>
                
            </Setter.Value>
        </Setter>
        </Style>
</Window.Resources>
 
    <Grid>
        <dg:DataGrid x:Name="dgItemList" AutoGenerateColumns="False"
                     
                     CanUserAddRows="False" CanUserDeleteRows="False" 
                     CanUserReorderColumns="False" CanUserResizeColumns="False"
                     CanUserSortColumns="False" SelectionUnit="Cell"
                     SelectionMode="Extended" HeadersVisibility="All"
                     RowHeaderWidth="30" RowHeight="30"
                     
                     ColumnWidth="SizeToHeader"
                     GridLinesVisibility="None">
            <dg:DataGrid.Columns>
                <dg:DataGridTemplateColumn Header="Ch1">
                <dg:DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <Button Content="{Binding Path = Ch1}"                                
                                Style="{StaticResource CustomRoundedButton}"/>
                    </DataTemplate>
                </dg:DataGridTemplateColumn.CellTemplate>
                </dg:DataGridTemplateColumn>
                <dg:DataGridTemplateColumn Header="Ch2">
                    <dg:DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Content="{Binding Path = Ch2}"                                
                                Style="{StaticResource CustomRoundedButton}"/>
                        </DataTemplate>
                    </dg:DataGridTemplateColumn.CellTemplate>
                </dg:DataGridTemplateColumn>
                <dg:DataGridTemplateColumn Header="Ch3">
                    <dg:DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Content="{Binding Path = Ch3}"
                                
                                Style="{StaticResource CustomRoundedButton}"/>
                        </DataTemplate>
                    </dg:DataGridTemplateColumn.CellTemplate>
                </dg:DataGridTemplateColumn>
                <dg:DataGridTemplateColumn Header="Ch4">
                    <dg:DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Button Content="{Binding Path = Ch4}"
                                
                                Style="{StaticResource CustomRoundedButton}"/>
                        </DataTemplate>
                    </dg:DataGridTemplateColumn.CellTemplate>
                </dg:DataGridTemplateColumn>
            </dg:DataGrid.Columns>
        </dg:DataGrid>
    </Grid>
</Window>
//////////////////////////////// XAML ////////////////////////////////////////////////////
 
 
//////////////////////////////// XAML.cs ////////////////////////////////////////////////////
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Data;
using Microsoft.Windows.Controls;
 
namespace ProgressGridTest {
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window {
        public Window1() {
            InitializeComponent();
 
            DataTable objDataTable = new DataTable("Progress");
            objDataTable.Columns.Add("Ch1", typeof(int));
            objDataTable.Columns.Add("Ch2", typeof(int));
            objDataTable.Columns.Add("Ch3", typeof(int));
            objDataTable.Columns.Add("Ch4", typeof(int));
 
            for (int nCount = 0; nCount < 10; nCount++) {
                DataRow objDataRow = objDataTable.NewRow();
                int nRowNumber = nCount + 1;
                objDataRow[0] = Convert.ToInt32(0 % nRowNumber);
                objDataRow[1] = Convert.ToInt32(1 % nRowNumber);
                objDataRow[2] = Convert.ToInt32(2 % nRowNumber);
                objDataRow[3] = Convert.ToInt32(3 % nRowNumber);
                
 
                objDataTable.Rows.Add(objDataRow);
            }
 
            dgItemList.ItemsSource = objDataTable.DefaultView;
            
        }
 
    }
}
//////////////////////////////// XAML.cs ////////////////////////////////////////////////////

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