如何在C#中使用EWS API设置类别标志颜色

using Microsoft.Exchange.WebServices.Data;

ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP2);
service.Credentials = new WebCredentials("email@example.com", "password");
service.Url = new Uri("https://outlook.office365.com/EWS/Exchange.asmx");

ItemView view = new ItemView(1);
FindItemsResults<Item> results = service.FindItems(WellKnownFolderName.Inbox, view);
if (results.Items.Count > 0)
{
    Item item = results.Items[0];
    item.Load();
    // 获取邮件项的ID
    ItemId itemId = item.Id;
    // 设置类别标志颜色
    item.Categories = "Red Category";
    item.Update(ConflictResolutionMode.AlwaysOverwrite);
}