How do I change the accent colour of a Xamarin.Forms UWP application?

Question

I am developing a Xamarin.Forms UWP application.

I am struggling to set the accent colour of my application. This is the colour that is used for certain

Answer 1

Here is the style code of FormsTextBox for UWP.

You need to override below styled colors:

<Setter Property="Foreground" Value="{ThemeResource SystemControlForegroundBaseHighBrush}" />
<Setter Property="Background" Value="{ThemeResource SystemControlBackgroundAltHighBrush}" />
<Setter Property="BackgroundFocusBrush" Value="{ThemeResource SystemControlBackgroundChromeWhiteBrush}" />
<Setter Property="BorderBrush" Value="{ThemeResource SystemControlForegroundChromeDisabledLowBrush}" />

So to change the colour of your textbox boarder brush you can add these ThemeResources to your App.xaml like so:

<Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.ThemeDictionaries>
            <ResourceDictionary x:Key="Light">
                <SolidColorBrush x:Key="SystemControlHighlightAccentBrush" Color="#ff0000" />
            </ResourceDictionary>
        </ResourceDictionary.ThemeDictionaries>
    </ResourceDictionary>
</Application.Resources>

Answer 2

You can define a style setter property in App.xaml

    <ResourceDictionary>    
        <Style TargetType="Button" x:Name="myNewButtonStyle">
            <Setter Property="Background" Value="{ThemeResource ButtonBackgroundThemeBrush}" />
        </Style>
    </ResourceDictionary>

Then use CustomRenderer for the controls you need to change colors

    protected override void OnElementChanged(ElementChangedEventArgs<Button> e)
    {
        base.OnElementChanged(e);
        if (this.Element != null)
        {
            this.Control.Style = Windows.UI.Xaml.Application.Current.Resources["myNewButtonStyle"] as Windows.UI.Xaml.Style;
        }
    }

in a similar way you would be able to use Themed Resource Dictionary key and apply. This code can be used to have native styles on Xamarin's control.