Possible Blown Head Gasket

This is the test I have done so far and it is only visual, but does not really match symptoms of a blown head. what is happening is the engine idles at nominal temperature then the temperature drops when the car is mobile, it then proceeds when sitting at the lights to go back to nominal but then there is this, there is bubbles in the radiator with the cap off and its fluffy, but still green it does not change color. there is no oil in the water as it is not milky and this happened after she had a hard run, is this a blown head gasket? I am not certain myself.