Here are THREE "static" techniques that are good to know about.

1. XAML x:Static

...
xmlns:local="clr-namespace:MyNameSpace"
...

<Label Text="{x:Static local:MyClass.MyGlobalValue}" />

public class MyClass
{
  public static string MyGlobalValue;
}

2. XAML StaticResource

<Label BackgroundColor="{StaticResource MyDarkColor}" />

In App.xaml:

<Application ...
  <Application.Resources>
    <Color x:Key="MyDarkColor">#112233</Color>
...

3. Instance property "proxy" of a static value.

This "trick" accesses a "static" via an "instance property". Thus, it looks like any other property, to other code (and XAML).

<Label BackgroundColor="{Binding MyDarkColor}" />

// In the class that `BindingContext` is set to:
public static Color MyGlobalValue;

public Color MyDarkColor => MyGlobalValue;

IF the static is in a different class:

// In the class that `BindingContext` is set to:
public SomeType MyDarkColor => Class1.MyGlobalValue;

...
public class Class1
{
  public static SomeType MyGlobalValue;
}