Why this does not set the background when is disabled? - wpf

Question

I have a button and I want to change the background, it must be red when is anabled and green when is disabled. It's only an example to understand why it does not work, and the difference between when it works and when it does not work.
Option 1: when I use triggers in the button:
<Button Content="Buscar" Height="23" Name="btnComponentesBuscar" Width="75">
<Button.Style>
<Style TargetType="Button">
<Style.Triggers>
<Trigger Property="IsEnabled" Value="True">
<Setter Property="Background" Value="Red"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Background" Value="Green"/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
OPTION 2: modifying the template of the button. In the resources dictionary of my control in which I have my button, I put this:
<Style x:Key="MyButtonCustomTemplate" TargetType="{x:Type Button}">
<Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
<Setter Property="Background" Value="{StaticResource Button.Static.Background}"/>
<Setter Property="BorderBrush" Value="{StaticResource Button.Static.Border}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Padding" Value="1"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border x:Name="border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="true">
<ContentPresenter x:Name="contentPresenter" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsDefaulted" Value="true">
<Setter Property="BorderBrush" TargetName="border" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Background" TargetName="border" Value="{StaticResource Button.MouseOver.Background}"/>
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.MouseOver.Border}"/>
</Trigger>
<Trigger Property="IsPressed" Value="true">
<Setter Property="Background" TargetName="border" Value="{StaticResource Button.Pressed.Background}"/>
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.Pressed.Border}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Background" TargetName="border" Value="Green"/>
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.Disabled.Border}"/>
<Setter Property="TextElement.Foreground" TargetName="contentPresenter" Value="{StaticResource Button.Disabled.Foreground}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="true">
<Setter Property="Background" TargetName="border" Value="Red"/>
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.Static.Border}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
In the second option it works as exepcted, but I would like to simplify the code and I see that the first option has less code, but I don't know why it does not work.
Thank so much.