<StackLayout Margin="20"
                     Spacing="20">
                <RadioButton x:Name="radioButton"
                             Content="Option 1"/>
                <Button Text="Set Background to Red"
                        Clicked="OnSetRedBackgroundClicked"/>
                <Button Text="Set Background to null"
                        Clicked="OnButtonClicked"
                        x:Name="button"
                        Padding="10"/>
                <Button Text="Set Background (Gredient)"
                        Clicked="OnSetBackgroundClicked"
                        x:Name="setBackgroundButton"
                        Padding="10"/>
        </StackLayout>

void OnSetBackgroundClicked(object sender, EventArgs e)
	{
		radioButton.Background = new LinearGradientBrush(
			new GradientStopCollection
			{
				new GradientStop { Color = Colors.Red, Offset = 0.0f },
				new GradientStop { Color = Colors.Blue, Offset = 1.0f }
			},
			new Point(0, 0),
			new Point(1, 1)
		);
	}
	void OnButtonClicked(object sender, EventArgs e)
	{
		radioButton.Background = null;
	}

	void OnSetRedBackgroundClicked(object sender, EventArgs e)
	{
		radioButton.Background = new SolidColorBrush(Colors.Red);
	}