The fire indicates a dynamic action. The white fire is the fire of aspiration,
the red fire is the
fire of renunciation and tapasya, the blue fire is the fire of spirituality and spiritual knowledge which purifies and dispels the Ignorance.
The fire you felt was the fire of purification and the heat came because it was burning up some resistance, after that was burnt out there was coolness and peace and quietude. The fire of course is the psychic fire which wells up from the veiled psychic source.
The fire is the divine fire of aspiration and inner tapasya. When the fire descends again and again with increasing force and magnitude into the darkness of human ignorance, it at first seems swallowed up and absorbed in the darkness, but more and more of the descent changes the darkness into light, the ignorance and unconsciousness of the human mind into spiritual consciousness.
The fear of the fire you saw is misplaced, for it is the fire of purifying Agni that you see burning and that does no harm; it only clears away what should not be there. That is why it is followed by a lightness or an emptiness. You have only to be quiet and let the fire do its work. The heat one feels at that time is not the heat of fever or any other morbid heat. Afterwards, as you felt, all becomes cool and light.