Vaidimir some people like myself went through this stage where we sense the energy of a person but are unable to define character vibration and even the emotional vibrations that emanates and translated in our brains' visual cortex. like bats who use echo location by sending out audio signals to define the shape of objects by the bouncing of sound waves, our energy can do the same. as a matter of fact all organic things, at least, are relative to each other, which allows us to bet grounded/connected to other forms in this physical realm. This colorless aura is just you perceiving energy like a sonar translating energy to a image in your visual cortex,like a blind person who uses tongue clicks to determine if object are in his path(this example is from national geographic's brain games which was a study on a blind person who exercised this ability from since he was a child).
Modern magick Practitioners promote the exercise of energy perception through meditation and visualization to be able to come to a self understanding/observation of energy flow/perception so that practitioners can be there own witness and testimony of how magick works and is working with you will in your personal life.
p.s Many relate the third eye with visual perception of energy but personally from my experience it is related all the higher senses of energy in that region(at least), senses such as hearing(ears) and scent(nose).