Various lights are manifested during meditation.In the beginning a bright light of the size of the pin point will appear in the forehead in the trikuti,which is called the 'Ajna chakra'. Different lights are seen when eyes are closed. These lights appear in mental space, and are tantric lights having it's specific colors. Frequently it is combination of white and yellow but red and blue lights are rarely seen. Initially small balls of light are seen which later become dazzling lights. 

The lights become stable with advancement of meditation. Also at higher stages of meditation figures as sadhus or other physical forms are seen in stable light.One should not pay much attention to these figures and should concentrate on the ultimate goal only. These are simply to make one convience that there is existence of God and super physical and meta physical realities. This is 'sadhana shakti'. If carried out with faith, one can achieve marvellous results, get siddhi and can benefit both the oneself and the mankind.