Multiple platform condition in XAML view - Xamarin forms [duplicate] - xamarin

Question

I have the following C# code:
var footer = new StackLayout()
{ BackgroundColor = Device.OnPlatform(Color.FromRgb(225, 240, 251), Color.FromRgb(225, 240, 251), Color.Black),
};
How can I translate that into Xamarin Xaml, more importantly the Device Platform specifics for the FromRgb?
I have the following XAML so far... again, it's the FromRgb that's stumping me.
<StackLayout.BackgroundColor>
<Color>
<OnPlatform x:TypeArguments="Color"></OnPlatform>
</Color>
</StackLayout.BackgroundColor>
UPDATE 14/02/2015
I've just tried the answer below and I have the following but it's not updating the background colour for either iOS or Windows Phone. If I add the Background Color to the root StackLayout element it works...:
<StackLayout HorizontalOptions="FillAndExpand">
<StackLayout.BackgroundColor>
<Color>
<OnPlatform x:TypeArguments="Color">
<OnPlatform.WinPhone>#51C0D4</OnPlatform.WinPhone>
<OnPlatform.iOS>#51C0D4</OnPlatform.iOS>
</OnPlatform>
</Color>
</StackLayout.BackgroundColor>
<Label Text=""></Label>
<StackLayout Orientation="Horizontal" VerticalOptions="EndAndExpand" HorizontalOptions="FillAndExpand">
<StackLayout Orientation="Horizontal" HorizontalOptions="CenterAndExpand">
<Button Text="Login"></Button>
<Button Text="Sign Up"></Button>
</StackLayout>
</StackLayout>
</StackLayout>

Answer 1

You're almost there. The default converter takes care of converting the color from either a named color (e.g. White, Red, etc.) or a hex color (e.g.: #FF0000).
<StackLayout.BackgroundColor>
<OnPlatform x:TypeArguments="Color">
<OnPlatform.iOS>#FF0000</OnPlatform.iOS>
<OnPlatform.Android>#00FF00</OnPlatform.Android>
</OnPlatform>
</StackLayout.BackgroundColor>

Answer 2

Newer version syntax of OnPlatform is slightly different
In Xaml:
<ResourceDictionary>
<OnPlatform x:Key="SwitchOnColor" x:TypeArguments="Color" >
<On Platform="iOS|Android" >#0000FF</On>
<On Platform="UWP">#FF0000</On>
</OnPlatform>
</ResourceDictionary>
In code:
switch (Device.RuntimePlatform)
{
case "iOS":
break;
case "Android":
break;
case "UWP":
break;
default:
break;
}

Answer 3

You can do this also:
<ContentView>
<OnPlatform x:TypeArguments="View">
<On Platform="iOS">
<Label Text="iOS" />
</On>
<On Platform="Android">
<Label Text="Android" />
</On>
</OnPlatform>
</ContentView>