[Flags]
public enum LightSignal
{
   None = 0,
   Blue = 0b00001,
   Red = 0b00010,
   White = 0b00100,
   Yellow = 0b01000,
   Green = 0b10000,

   TypeA = Blue | Red | Green | White,
   TypeB = Red | Green,
   TypeC = Yellow | Green,
   TypeLastToB = Red | Blue
}

public enum EventType
{
   Unknown,
   A,
   B,
   C,
   RenameLastToB
}

public EventType CalcEvent(LightSignal ls)
{
   if(LightSignal.TypeA == ls) return EventType.A;
   if(LightSignal.TypeB == ls) return EventType.B;
   if(LightSignal.TypeC == ls) return EventType.C;

   if((LightSignal.TypeLastToB & ls) == LightSignal.TypeLastToB) return EventType.RenameLastToB;

   return defauit;
}