I agree that theoretically when using the Kelvin scale it would be - 136.575 °C. But using the Fahrenheit scale the same way to calculate the answer as you did with the Kelvin scale you would get -8,9 °C ( 0 °C = 32 °F, 16 °F = -8,9 °C).
So two different answers, I think the major problem is the word colder as you said yourself. There isn't really a scale that determines how cold your body feels, there is off course windchill, not the real temperature your thermometer shows but the temperature that your skin "feels" due to the force of the wind and the temperature.
I would say a great question, but I think it will be very difficult to answer!