Concealed round the back of Dominique Lévy's first-floor Bond Street gallery is a typical photo-painting from Gerhard Richter’s mid-1960s greyscale period. It is out of place in this gathering of the artist’s Colour Charts, a dozen colour-block paintings inspired by a Ducolux paint-sample card from a Düsseldorf hardware store.

But it is the big surprise of this Frieze-season show, curated by Lock Kresler. Kresler has mounted it perpendicular to the wall, like a pub sign, so you can see the reverse: a grid of reds in various shades. Back in 1965 when he painted it, Richter was reacting against Pop by experimenting with non-figurative, non-emotional colour compositions. But the artist harboured second thoughts about revealing such a brazen 'readymade' at that moment. Against the wall it went.

The suite of reds is the first evidence of the Richter most of us know. The following year – in an exhibition at Munich’s Galerie Friedrich & Dahlem that was violently criticised – he would unveil 19 such paintings, starting with 192 Colours, a grid of Ducolux squares 12 down and 16 across. This canvas is the most textural and painterly in the series, as Richter used sweeping brushstrokes with the oils he’d become used to in his work. The others are painted in a more neutral industrial lacquer, yet, says Levy, 'seeing them all together, they way they relate to each other, there’s a musicality. The togetherness is important.'

This is the first exhibition since 1966 to gather so many Colour Charts together in one place. Kresler has even included an original Ducolux chart in a mini-exhibit of source materials. By the 1970s, Richter had abandoned his colour-blocking for a different sort of multi-coloured abstract art. But the Colour Chart series was his entrée, too good to face the wall.