This work is published on the occasion of the exhibition "Signac, les couleurs de l'eau" presented the musée des impressionnismes in Giverny, from March 29 to July 2, 2013. The description of the water and sky offered by Paul Signac (1863-1935) was an inexhaustible excuse to multiply the color variations. Like Monet, Signac indeed is a constant source of inspiration in the evocation of water and colors. The reflection of light on the surface of the river and the sea are the real fragments, and the artist, ardent defender of pure color, found in this pattern a natural illustration of neo-Impressionist theory of the division of tones.