Xamarin Form 4 Shell - xamarin.forms

Question

I start an new projet with the new Shell from Xamarin Form 4. I try to found a way to control the appearance when a FlyoutItem is disable. On the style with the sample, the BaseStyle control the apparence of the Shell himself (title bar tab bar, ...) But the Shell.disableColor is for the shell himself not the flyoutItem text. Any idea?
<Shell.Resources>
<ResourceDictionary>
<Color x:Key="NavigationPrimary">#2196F3</Color>
<Style x:Key="BaseStyle" TargetType="Element">
<Setter Property="Shell.BackgroundColor" Value="{StaticResource NavigationPrimary}" />
<Setter Property="Shell.ForegroundColor" Value="White" />
<Setter Property="Shell.TitleColor" Value="White" />
<Setter Property="Shell.DisabledColor" Value="#95FFFFFF" />
<Setter Property="Shell.UnselectedColor" Value="#95FFFFFF" />
<Setter Property="Shell.TabBarBackgroundColor" Value="{StaticResource NavigationPrimary}" />
<Setter Property="Shell.TabBarForegroundColor" Value="White"/>
<Setter Property="Shell.TabBarUnselectedColor" Value="#95FFFFFF"/>
<Setter Property="Shell.TabBarTitleColor" Value="White"/>
</Style>
<Style x:Key="FAIcon" TargetType="Label">
<Setter Property="VerticalTextAlignment" Value="Center"/>
<Setter Property="FontFamily" Value="{StaticResource FARegular}"/>
<Setter Property="FontSize" Value="{StaticResource BigSize}"/>
<Setter Property="TextColor" Value="#FF000000"/>
</Style>
<Style x:Key="ItemText" TargetType="Label">
<Setter Property="VerticalTextAlignment" Value="Center"/>
<Setter Property="FontFamily" Value="{StaticResource SourceSansProRegular}"/>
<Setter Property="FontSize" Value="{StaticResource BigSize}"/>
<Setter Property="TextColor" Value="#FF000000"/>
</Style>
</ResourceDictionary>
</Shell.Resources>
<Shell.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="45"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.2*" />
<ColumnDefinition Width="0.8*" />
</Grid.ColumnDefinitions>
<Label Margin="15,0,0,0" Text="{Binding FlyoutIcon}" Style="{StaticResource FAIcon}" />
<Label Grid.Column="1"
Text="{Binding Title}"
Style="{StaticResource ItemText}"/>
</Grid>
</DataTemplate>
</Shell.ItemTemplate>
<Shell.FlyoutHeader>
<Grid HeightRequest="180" BackgroundColor="{StaticResource DarkGreyColor}">
<Image Source="KelvinSplash1.png"
Aspect="AspectFill"
HeightRequest="180"
HorizontalOptions="FillAndExpand" />
<Label Text="Kelvin Mobile"
TextColor="White"
FontSize="32"
HorizontalOptions="Center"
VerticalOptions="Center"
HorizontalTextAlignment="Center"
VerticalTextAlignment="Center" />
</Grid>
</Shell.FlyoutHeader>
<FlyoutItem Icon=""
Title="Accueil">
<ShellContent Route="Home" ContentTemplate="{DataTemplate views:HomePage}" />
</FlyoutItem>
<FlyoutItem Icon=""
Title="Division: Solmec" IsEnabled="false">
</FlyoutItem>
<FlyoutItem Icon=""
Title="Fonctions">
</FlyoutItem>
<FlyoutItem Icon=""
Title="À Propos"
IsEnabled="False">
<ShellContent Route="About" ContentTemplate="{DataTemplate views:AboutPage}" />
</FlyoutItem>