Luminosity is a quality of the consciousness, the one that perceives without an "I," self, or egotistical condition, without intermediary. It is simply a state of direct perception without the need to think, rationalize, sentimentalize, or act from impulsiveness.
The gateway to real meditation begins with self-observation, which is a form of light. Whether or not you see specific colors, consciousness is a form of seeing and understanding, a qualitative state that develops more and more in us when we learn to pay attention and to relax our three brains. Meditation unfolds as we discover the presence of divinity and maintain awareness in each moment of our existence. This is well explained by an instructor in Chicago who gave a course of Gnostic Psychology; see specifically the lecture called "The Light of the Consciousness."
Joyful in hope, suffering in tribulation, be thou constant in thy prayer.
Benedictis, qui venit in nomine Domini. Osanna in excelsis.
"Blessed is he who comes in the name of the Lord. Hosanna in the highest!"