Light is how we see, and in its absence we don't. All works are therefore, to some degree or other, about light. Works on paper seem especially blessed in this respect since they are washed in the pure paper light, and they never forget it. There are even individuals who devote themselves entirely to this light, and only seek to magnify it. We face their works as we face the sun and stars.
Color is one of the joys of light, and of living.
It is often how we know things and enjoy them. Paper gives life to color almost like light itself and here again there are those whose devotion has been primarily to light through color. It is as stained glass. In a drawing or watercolor we see things reduced to shape, and experience that this is how we sense, feel, and know things. In works on paper we can see these things so directly, so simply and clearly, with reason.