Change the main style colors for the app

Styles.xaml

    <Color x:Key="AppAccentColor">#3498db</Color>
    <SolidColorBrush x:Key="AppAccentColorBrush" Color="{StaticResource AppAccentColor}" />
    <Color x:Key="AppAccentLightColor">#2980b9</Color>
    <SolidColorBrush x:Key="AppAccentLightColorBrush" Color="{StaticResource AppAccentLightColor}" />
    <Color x:Key="AppAccentForegroundColor">#333333</Color>
    <SolidColorBrush x:Key="AppAccentForegroundColorBrush" Color="{StaticResource AppAccentForegroundColor}" />
    <Color x:Key="AppAccentBackgroundColor">#FFE6E6E6</Color>
    <SolidColorBrush x:Key="AppAccentBackgroundColorBrush" Color="{StaticResource AppAccentBackgroundColor}" />
    <Color x:Key="BusyIndicatorBackgroundColor">#7F000000</Color>
    <SolidColorBrush x:Key="BusyIndicatorBackgroundColorBrush" Color="{StaticResource BusyIndicatorBackgroundColor}" />
    <x:Double x:Key="HighResolutionImageSideLength">1000</x:Double>