The normal temperature of my car is about 80 - 90 degrees. The temperature fluctuations that you describe while driving in traffic are normal. Your car is at an age where it would be a good idea to have the cooling system serviced, flushing the radiator, replacing the thermostat and adding new coolant. I would have thought it would be on the underside of the radiator. Do not do this with the engine hot as you could get scalded.
Water is clear clean coolant green.
Foam is clear clean white. I notice no leaks. However, I am always having to add water to the radiator. Much steam from rear tail pip in the mornings. I have been smelling the radiator water.