I completely agree with Nikki about grammar; it can be used in exactly this way in English. You can have a grammar of painting, of music, of dance, of acting, as well as of language. As for "particulière", well, I think you could interpret it as distinctive/unusual (or particular or special) or as personal (specific to that particular artist). I'm not sure which way to take it; I think either could be defended, and there are five or six defensible translations of this word in this context.

However I must strongly disagree over "picturalité". I wouldn't be surprised if "pictural" is sometimes used in French in the way "pictorial" (or more rarely "pictural") is used in English: that is, to mean related to pictures. But if and when it is, it is a calque of English. The word does not properly have this meaning in French. Look in any good French monolingual dictionary: the Trésor, Robert, Larousse... The only meanings are "related to painting" or "possessing the quality of painting". In other words, in French it relates to the medium, and in English it relates to representation or depiction, in any medium, not necessarily painting.

In my opinion it is inconceivable that the word is being used here in its English sense, that is, to mean pictoriality (I don't think "picturality" exists in English; I can't find it in any dictionary). I just don't believe that an French art critic or historian would use it like that, and far less in relation to Alan Green, an abstract painter whose work contains no representation at all, just form and colour.

Here are some examples of his work:
http://www.artnet.com/artists/alan-green/

And this is from his Guardian obituary:

"A painting such as Double Crimson Painting (1978) was precisely that, but the two halves of the painting were treated in opposition, one in glossy oils, one in matt tempera, one with a textured surface broken up by darker diagonal brush strokes, one smooth. The finished work has that sense of inevitable conclusion that marks all Green's art - the result of a process of reduction, scraping away paint and starting again, building up and scraping back. [...]
His painting went through successive phases, moving from atmospheric blocks of colour to big canvases with single colours apparently gently vibrating, and on to wide slabs of colour on huge surfaces. [...]
https://www.theguardian.com/news/2003/may/28/guardianobituar...

In other words, Alan Green was preeminently what is known as a "painterly" painter. And that is what "pictural" means: painterly.

"Painterly" is a term that goes back to Wölfflin and his distinction between painterly (malerisch) and linear painters. See here for a quick introduction:

"Painterliness is a concept based on the German term malerisch (painterly) [...]
The Impressionists, Fauvists and the Abstract Expressionists tended strongly to be painterly movements.
Painterly art often makes use of the many visual effects produced by paint on canvas such as chromatic progression, warm and cool tones, complementary and contrasting colors, broken tones, broad brushstrokes, sketchiness, and impasto."
https://en.wikipedia.org/wiki/Painterliness

And here's the equivalent distinction in French:

"Double portrait : le « pictural » et le « linéaire »"
http://theses.univ-lyon2.fr/documents/getpart.php?id=lyon2.2...

Given the proper sense of "pictural" as "painterly" in art theory, and given the supremely painterly qualities of Green (blocks of colours rather than contours, strong emphasis on surface texturality), I think it is certain that "picturalité" here has its usual meaning (in art discourse) of "painterliness".

An alternative would be simply "a grammar of painting", but I think that's too broad, for the reasons I've outlined.

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Note added at 6 hrs (2016-09-20 00:52:25 GMT)
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I think it would be difficult to find a painter to whom the English word "pictorial" is less applicable than Alan Green.

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Note added at 13 hrs (2016-09-20 08:02:37 GMT)
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Sorry to bang on, but seriously, "picturality" simply won't do; it's plain wrong. If it exists at all, it's a synonym of "pictoriality", since pictural is a synonym of pictorial in English (dictionaries are unanimous). And that means related to pictures. And pictures are simply images: drawings, painting, photographs, images on a screen... A "grammaire de la picturalité" is not a grammar of pictures or of the nature of pictures.

Here's a quotation that confirms what I've been saying about "picturalité" meaning what is called "painterliness": the properties of painting as a medium, not its representational properties. It's from Denys Riout in an essay entitled "La peinture contre les images", and is quoted right at the start of this text:

"La photographie « aide à comprendre en quoi la peinture se distingue de l'image, et plus radicalement encore, s'oppose à elle, déjoue sans cesse sa transparence. Ce qui résiste à la transformation des agencements de la pâte colorée en image, icône, et qui nous attire, c'est la picturalité, autrement dit les qualités spécifiques de la pâte elle-même, alors objet du monde et non pas face signifiante du signe"
http://www.persee.fr/docAsPDF/ameri_0982-9237_1988_num_3_1_9...