Paul Signac: Tone

“Of the three primary colors, the three binary ones are formed. If you add to one of these the primary tone that is its opposite, it cancels it out. This means that you produce the required half-tone. Therefore, adding black is not adding a half-tone, it is soiling the tone whose true half-tone resides in this opposite me have just described. Hence the green shadows found in red. The heads of the two little peasants. The yellow one had purple shadows; the redder and more sanguine one had green ones.”

Paul Signac

Quoted by Maria Buszek, online - note 19 http://mariabuszek.com/mariabuszek/kcai/Expressionism/Readings/SignacDelaNeo.pdf
The notebook where this sentence appears was only published, in facsimile, in 1913 by J. Guiffrey. Signac therefore must have consulted it at the Conde Museum, in Chantilly. This Moroccan travel document was bought at the Delacroix sale by the painter Dauzats for the Duc of Aumale.
From Delacroix to Neo-Impressionism, 1899

Color

“Pissarro wants to achieve delicacy by means of adjustments of nearly like tones; he keeps from juxtaposing two distant tones and does without the vibrant note which such contrast gives, but strives on the contrary to diminish the distance between two tints by introducing into each one of them intermediate elements which he calls 'passage'. But the neo-impressionist technique is based precisely on this type of contrast, for which he feels no need, and on the violent purity of tints which hurts his eye. He has kept of divisionism only the technique, the little dot, whose raison d'etre is exactly that it enables the transcription of this contrast and the conservation of this purity. So it is easy to understand why he [Pissarro] gave up this means, insufficient as it is by itself.”

Paul Signac

As quoted by John Rewald, in Camille Pissarro - Letters to His Son Lucien ed. John Rewald, with assistance of Lucien Pissarro; from the unpublished French letters; transl. Lionel Abel; Pantheon Books Inc. New York, second edition, 1943, pp. 135
Signac, in his book De Delacroix au Neo-impressionnisme, tried to explain in this way Camille Pissarro's desertion from Neo-Impressionism around 1890
From Delacroix to Neo-Impressionism, 1899

Feeling , Understanding , Distant , Hurt

“It seems that the first consideration of a painter who stands before the white canvas should be to decide what curves and arabesques should cut the surface, what tints and tones should cover it... Following the precepts of Delacroix he would not begin a composition until he had first determined its organization. Guided by tradition and by science, he would adjust the composition to his conception, that is to say he would adapt the lines (directions and angles), the chiaroscuro (tones), the colors (tints), to the traits he wished to make dominant.”

Paul Signac

Chapt. III.; as quoted by John Rewald, in Georges Seurat', a monograph https://ia800607.us.archive.org/23/items/georges00rewa/georges00rewa.pdf; Wittenborn and Compagny, New York, 1943. p. 21
From Delacroix to Neo-Impressionism, 1899

Color , Science

“Neo-Impressionist method is an attempt is made to achieve the richness of the sunlight spectrum with all its tones. An orange that blends with yellow and red, a violet that tends toward red and blue, a green between blue and yellow are, with white the sole elements. Through mixture (in the eye of the observer) of these pure colours, whose relationship can be varied at will, from the most brilliant to the greyish. Every brush stroke that is taken from the palette remains pure on the canvas.”

Paul Signac

From Delacroix to Neo-Impressionism, 1899

“We have never heard Seurat, Cross, Luce, Van de Velde or indeed Van Rysselberghe or Angrand speak of dots. We have never seen them be preoccupied by Pointillism. Read these lines, dictated by Seurat to Jules Christophe, his biographer: 'Art is harmony; harmony is the analogy between opposites and between similar elements of tone, tint and line. By tone I mean light and dark; tint is red and its complementary: green, orange and its complementary: blue, yellow and its complementary: purple... The method of expression relies on the optical mixture of tones, tints and their reactions”

Paul Signac

shadows that follow very strict rules
Quote from Maria Buszek, online - note 22 http://mariabuszek.com/mariabuszek/kcai/Expressionism/Readings/SignacDelaNeo.pdf
Seurat's quote from: Jules Christophe, Seurat, in 'Les Hommes d'aujourd'hui', no. 368, March-April 1890
From Delacroix to Neo-Impressionism, 1899

Art , Light , Reading