A blank sheet of regular print paper is positionned in the center of the frame. Lights are hidden in the frame edges and illuminate the paper from the sides with a grazing incidence. Color filters are placed in front of the lights. This results in a color gradient on the paper (see picture bellow for a flat sheet of paper). Because the paper is slightly folded, different regions are more or less exposed to the light: the paper appears to change color between folds.
It is easy to change to color filters, the sides illumination is coming from or the shape of the paper folds. This allows for a lot of variation in the resulting design.