using (var pst = PersonalStorage.Create("storage.pst", FileFormatVersion.Unicode))
{
    // Create a standard Contacts folder with the IPF.Contacts container class.
    var contacts = pst.CreatePredefinedFolder("Contacts", StandardIpmFolder.Contacts);
    
    // An exception will not arise. EnforceContainerClassMatching is false by default.
    contacts.AddSubFolder("Subfolder1", "IPF.Note");
    
    // An exception will occur as the container class of the subfolder being added (IPF.Note) 
    // does not match the container class of the parent folder (IPF.Contact).
    contacts.AddSubFolder("Subfolder3", new FolderCreationOptions {EnforceContainerClassMatching = true, ContainerClass = "IPF.Note"});
}

using (var olm = OlmStorage.FromFile("storage.olm"))
{
    var categories = olm.GetCategories();
    
    foreach (var category in categories)
    {
        Console.WriteLine($"Category name: {category.Name}");
        
		//Color is represented as a hexadecimal value: #rrggbb
        Console.WriteLine($"Category color: {category.Color}");
    }
}

foreach (var msg in olm.EnumerateMessages(folder))
{
    if (msg.Categories != null)
    {
        foreach (var msgCategory in msg.Categories)
        {
            Console.WriteLine($"Category name: {msgCategory}");
            var categoryColor = cat.First(c => c.Name.Equals(msgCategory, StringComparison.OrdinalIgnoreCase)).Color;
            Console.WriteLine($"Category color: {categoryColor}");
        }
    }
}