Light is color. Painting light means depending on colors - how you handle them, how well-tuned your instincts are, and looking. Unfortunelty, understanding how to paint light means understanding how to paint in general. It is all connected.
hibbary wrote a terrific article called Thinking in 3D that I highly recommend everyone who want to improove on their artworks to read - its content very much applies to how you have to think when it comes to painting light. Light is three dimensional, it moves and bounces and hits shapes at various angles depending on where it comes from. If you do not think about this in a three dimensional room, your will not be able to grasp the idea of light and how to put it into a picture. In a way you migth say that the key to understanding light and putting it into your paintings, is to think in 3D.
I've tried to analize the different parts of painting with different kind of light, to find a red t