Helene Kröller-Müller was a woman with a vision. The daughter of a wealthy industrialist and the wife of another, she was one of the first women to assemble a major art collection. Whereas most collectors of her era aimed for breadth, building up a comprehensive range of representative works from different periods, Kröller-Müller focused, instead, on individuals and schools, prioritising what she called ‘thinking artists’ of her own time. She bought many of Van Gogh’s works and was an early champion of the artistic school known as ‘Neo-Impressionism’, purchasing major pieces by Seurat, Signac and their contemporaries before leading galleries had recognised their importance.

Over 30 artworks from Kröller-Müller’s collection (on loan while the Kröller-Müller Museum in the Netherlands undergoes renovation) form the core of the National Gallery’s Radical Harmony exhibition. The two big names are well represented, but so too are lesser-known artists from the Low Countries, such as Jan Toorop, Théo van Rysselberghe and Anna Boch. Several were associated with the Belgian artistic movement known as Les XX, which helped to disseminate Neo-Impressionism beyond France, and all adopted the ‘Pointilliste’ technique (though some eschewed the label). The Kröller-Müller loans are supplemented by around 25 complementary works from other collections, reuniting some originally conceived in pairs. Toorop’s Evening (Before the Strike) and Morning (After the Strike) (1888-90), for example, depict a married couple’s anguish and then the wife’s devastated resignation, as her husband’s corpse is borne aloft.

Such images chime with the ‘radical’ framing of the exhibition. Signac, Toorop, and the French painter Maximilien Luce shared sympathies with the anarchist-communist movement of the late 19th century and depicted workers in idealised, utopian settings. Signac’s chalk-drawn study for ‘In The Time of Harmony’ (1893-95), for instance, shows workers picking figs and resting in the shade beside the Mediterranean: he later painted a mural on the subject for the town hall of a working-class Parisian banlieue. Luce’s The Iron Foundry (1899), a quasi-Futurist representation of labourers silhouetted against a background of fire and cloud, meanwhile, was displayed for many years in the office of Kröller-Müller’s wealthy husband, something of a champagne socialist avant la lettre, it would seem.

Are curatorial claims of artistic radicalism overstated? Neo-Impressionism certainly had its innovations. It set about reappraising Impressionism, taking a quasi-scientific approach to light and optics by using dots of pure colour that merge to form a coherent whole, rather like pixels. The gradual shift away from ‘the dot’ to large daubs and swirls is clearly traced here, the latter most striking in Woman Sewing (1891) by Henry van de Velde, later the architect of Kröller-Müller’s Museum. But anyone expecting any truly revolutionary modern art from this exhibition may be disappointed. The largest proportion of paintings, placed in rooms at the beginning and end, are beach and harbour scenes and other landscapes in muted palettes that create an impression of utmost serenity and stillness, more calming than challenging.

Far more dynamic is the exhibition’s star attraction, Chahut (1889-90), the first major work by Seurat that was acquired for public display, and a canny purchase by Kröller-Müller, who made the mistake of not buying A Sunday on La Grande Jatte. Chahut is a stylised image, full of movement, which draws the eye upwards with the high kicks of the can-can dancers and the conductor’s raised baton. Chahut has been hung effectively to place us, the viewers, on a level with the double-bassist whose back is turned towards us, but also in uncomfortable proximity to the voyeur at bottom right, a seedy individual with a grotesque rouged smile, snout-like nose, and hat positioned low to preserve his anonymity. Several other paintings of working-class entertainment have been hung nearby: a café-concert by Pissarro; a bullfight at the Paris World’s Fair by Henri-Edmond Cross. These, too, are painted from the perspective of an audience member: we are invited to imagine ourselves not as bourgeois art collectors or viewers but as part of la foule.

The Neo-Impressionists’ ground-breaking use of colour is, as one would expect, a major theme of the exhibition, and the first image we are presented with is of a colour wheel, to illustrate the way in which these artists juxtaposed shades from opposite sides of the spectrum to maximise luminosity and vibrancy. Signac’s Collioure, the Belltower, Opus 164 (1887) – one of Kröller-Müller’s first purchases – is a prime example, a scene of a coastal village that uses delicate blues and peaches to create an impression of glowing light. Unfortunately, the curators of Radical Harmony have not been quite as attentive to the subtleties of colour as the artists. They purport to have adopted Kröller-Müller’s approach (unusual at the time) of using white walls as a neutral backdrop against which to display the Neo-Impressionists’ dazzling hues. But the paint used in London is not so much white as a pale grey that flattens rather than flatters the shades set against it.

Elsewhere, the colour-scheme goes to the opposite extreme with the choice of a deep purple (the shade of cardinals’ vestments or chocolate wrappers, according to taste). This works with varying degrees of success. Van Rysselberghe’s arresting portrait of his wife Maria, who holds our gaze assertively as she poses in tangerine silk in front of a vase of gaily coloured chrysanthemums, pops out against this background. By the same artist, Maria Sèthe at the Harmonium, in which the sitter is clad in dark mauve against a yellow instrument, looks sickly, almost psychedelic.

The hang may be a little hit and miss, then, and the claims of radicalism a touch exaggerated, but there is a great deal to enjoy in this exhibition. Particularly interesting are the portraits of artists, musicians, writers, women’s rights campaigners and academics from turn-of-the-century Brussels: a vibrant yet long-forgotten intellectual milieu. Kröller-Müller herself emerges as an inspiring figure: from an art appreciation course, taken with her child, sprang the idea for a magnificent collection, intended not for personal pleasure but for the education and edification of the public. A noble venture indeed.