Meeting.cs

    public class Meeting
    {
        private string _subject;

        public string Subject
        {
            get => _subject;
            set
            {
                if (value == _subject) return;
                _subject = value;
                switch (_subject)
                {
                    case "General Meeting":
                        Color = Xamarin.Forms.Color.FromHex("#7BC667");
                        break;
                    case "Release Retrospective":
                        Color = Xamarin.Forms.Color.FromHex("#9466F2");
                        break;
                    case "Sprint Meeting":
                        Color = Xamarin.Forms.Color.FromHex("#37AA97");
                        break;
                    default:
                        Color = Xamarin.Forms.Color.FromHex("#4C3AB9");
                        break;
                }
            }
        }

        public string Location { get; set; }

        public Xamarin.Forms.Color Color { get; set; } = Xamarin.Forms.Color.FromHex("#7BC667");

        public DateTime StartTime { get; set; }

        public DateTime EndTime { get; set; }

        public Meeting(string subject, string location, DateTime startTime)
        {
            Subject = subject;
            Location = location;
            StartTime = startTime;

            EndTime = StartTime.AddHours(1);
        }
    }

Thank you for notifying @JogyBlack. I have changed it.