App.xaml

<?xml version="1.0" encoding="utf-8" ?>
<Application x:Class="SampleApplication.App"
             xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">

    <Application.Resources>
        <ResourceDictionary>
            <!--  TODO: Share this resource dictionary between apps  -->
            <OnPlatform x:Key="ButtonFont"
                        x:TypeArguments="Font"
                        Android="Medium"
                        iOS="Small" />
            <OnPlatform x:Key="HeaderFont"
                        x:TypeArguments="Font"
                        Android="Large"
                        WinPhone="Large"
                        iOS="Large" />
            <OnPlatform x:Key="PrimaryTextColor"
                        x:TypeArguments="Color"
                        Android="White"
                        WinPhone="White"
                        iOS="White" />
            <OnPlatform x:Key="SmallFontSize"
                        x:TypeArguments="x:Double"
                        Android="10"
                        WinPhone="12"
                        iOS="10" />
            <OnPlatform x:Key="RegularFontSize"
                        x:TypeArguments="x:Double"
                        Android="15"
                        WinPhone="20"
                        iOS="15" />
            <OnPlatform x:Key="LargeFontSize"
                        x:TypeArguments="x:Double"
                        Android="30"
                        WinPhone="40"
                        iOS="30" />
            <OnPlatform x:Key="MediumFontSize"
                        x:TypeArguments="x:Double"
                        Android="20"
                        WinPhone="30"
                        iOS="20" />

            <OnPlatform x:Key="CardHeight"
                        x:TypeArguments="x:Double"
                        Android="100"
                        WinPhone="100"
                        iOS="100" />

            <OnPlatform x:Key="CardImageHeight"
                        x:TypeArguments="x:Double"
                        Android="90"
                        WinPhone="90"
                        iOS="90" />

            <!--  Same colors that are in the android color resource and static class ColorResources  -->
            <Color x:Key="PrimaryDark">#2286C4</Color>
            <Color x:Key="Primary">#2C92D1</Color>
            <Color x:Key="PrimaryLight">#2C92D1</Color>
            <Color x:Key="Text">#FFFFFF</Color>
            <Color x:Key="Icons">#FFFFFF</Color>
            <Color x:Key="WindowBackground">#F5F5F5</Color>
            <Color x:Key="Accent">#EE2B89</Color>
            <Color x:Key="PrimaryText">#212121</Color>
            <Color x:Key="SecondaryText">#727272</Color>
            <Color x:Key="Divider">#B6B6B6</Color>
            <Color x:Key="Alarm">#DC595F</Color>

            <Thickness x:Key="FormPadding">12,5,12,0</Thickness>

            <Style x:Key="MyButtonStyle" TargetType="Button">
                <Setter Property="TextColor" Value="Black" />
                <Setter Property="BackgroundColor" Value="Pink" />
                <Setter Property="BorderWidth" Value="1" />
                <Setter Property="BorderRadius" Value="3" />
                <Setter Property="BorderColor" Value="#ADADAD" />
                <Setter Property="Font" Value="{StaticResource ButtonFont}" />
            </Style>
        </ResourceDictionary>
    </Application.Resources>
</Application>