(...)

Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine("");
Console.WriteLine(":: ALL VALID ::");

ISpecification<Person> validSpecification = new PersonValidSpecification<Person>();

var validPeople = people.Where(x => validSpecification.IsSatisfiedBy(x));

foreach (var item in validPeople)
{
    Console.WriteLine(item.PersonId + " | " + item.Name + " | " + item.Email.Address + " | " + item.Category?.Description);
}

(...)