Set background color on mouse hover in comboboxitem WPF control

I am creating a WPF project .I am trying to remove this default background [marked in orange] on mouse hover from the combobox drop down. Below is the code which I have trying. I have tried multiple solutions available at various posts but the background color does not seems to change. Thanks a lot in advance for the help !!

 <ComboBox HorizontalAlignment="Left" Margin="95,44,0,0" VerticalAlignment="Top" Width="208">
            <ComboBox.Resources>                
                    <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" 
                        Color="Gray"/>               
                    <Style TargetType="{x:Type ComboBoxItem}">
                    <Setter Property="Foreground" Value="Gray" />
                    <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
                    <Setter Property="BorderThickness" Value="0"/>
                    <Setter Property="OverridesDefaultStyle" Value="True"/>
                    <Style.Triggers>
                        <Trigger Property="IsFocused" Value="True">
                            <Setter Property="Background" Value="#FFCDCDCD"/>
                        </Trigger>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Background"  Value="Red"/>
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </ComboBox.Resources>
</<ComboBox>