Sri Aurobindo
Letters of Sri Aurobindo
Volume III - Part 2
These lights and visions are not hallucinations. They indicate an opening of the inner vision whose centre is in the forehead 
between the eyebrows. Lights are very often the first thing seen. Lights indicate the action or movement of subtle forces belonging to the different planes of being,– the nature of the force depending on the colour and shade of the light. The sun is the symbol and power of the inner or higher Truth – to see it in meditation is a good sign. The sea is also often symbolic, indicating usually the vital nature, sometimes the expanse of consciousness in movement. The opening of vision must be allowed to develop, but too much importance need not be given to the individual visions unless or until they become evidently symbolic or significant or shed light on things in the sadhana etc.