VeloeMonitorAvaloniaApp/VeloeMonitorApp/App.axaml

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:themes="clr-namespace:Material.Styles.Themes;assembly=Material.Styles"
			 x:Class="VeloeMonitorApp.App"
             RequestedThemeVariant="Default">
             <!-- "Default" ThemeVariant follows system theme variant. "Dark" or "Light" are other available options. -->

    <Application.Styles>
		<themes:MaterialTheme BaseTheme="Dark" PrimaryColor="Blue" SecondaryColor="LightBlue" />
    </Application.Styles>
</Application>