You'll soon see that, in terms of purchasing an effective souvenir of the show, your pounds 17.50 has been wasted. It's not just that none of the colour reproduction is precisely right. It's that, with Heron's work, when you lose the precise colour, you lose just about everything. Still, the exercise needn't be wholly negative. Noting the discrepancies may also attune the eye more keenly to what is going on. And something certainly is.
Patrick Heron's world of colour - welcome to it! Here's 60 years of work. We begin with the artist's very precocious late teens (a superb Matisse pastiche, for one thing), and proceed through other influences (Bonnard, Braque), to a pretty sudden jump in the mid-Fifties into pure abstraction - fields of luminous dobs. And after that there's freely brushed stripes, vertical and horizontal moving then into floating squares and discs, and then into the "wobbly hard-edged" period of the Sixties and Seventies, and then into something much looser and more gestural, and then to the scribbly, doodly stuff with lots of white and slightly more representational (inklings of his celebrated garden in Cornwall) that he's still doing now, in his late seventies...
But having said that, having described the changing forms of Heron's art mainly in terms of the shapes and structures and strokes it uses, is there anything more to say? For these changes of form have had a constant focus: the deployment of colour. As Heron once said, "Colour is both the subject and the means, the form and the content, the image and the meaning, in my paintings." And if colour is famously reproduction-proof, it is also famously beyond words. Faced with this array, can any of us do more than go mmm and aaah and hmph and uh?
Heron himself has been, in his time, a man of words, a highly intelligent and sensitive writer on modern art and an eloquent propagandist for one sort of modern art in particular - an art whose business is pure visual sensation, whose great aim is pleasure, an art for whom "decorative" is not a term of abuse but a term of high praise, an art of colour. But written arguments aside, the paintings themselves are argumentative. And no one, I think, just looking at them, would call them "decorative" in the slighting sense of the word. They don't look like decor. They look like paintings that earnestly believe in the power of sheer, unadulterated colour.
And yet for the wrong sort of viewer, how powerless that power is. And I confess: I am that wrong sort of viewer. I stand before this art of pleasure and more often that don't get much pleasure from it. You can try to incite agreement, of course. You can say, for instance, that the wobbly hard-edged period seems to be pure Carnaby Street and, incidentally, how odd to find this metropolitan tang in the Cornishman's work - but however you put it, it's a pretty horrible lot of colours. Isn't it?
You can try to find explanations too. You can wonder if perhaps there's a too obvious equation going on between pleasure and strong bright colours. Or does Heron's whole idea of an art dependent on pure visual sensation involve a jumped conclusion? The colours of Matisse and Bonnard managed such intensity, perhaps, just because colour for its own sake wasn't all those artists were thinking about. They sound plausible lines of argument - but how feeble they would be seem to someone who unreflectingly adored this work. You go aah, I go ugh, let's call the whole thing off.
But all isn't quite lost. For beyond immediate reactions, there's another level on which the paintings operate. This is the way in which colour- areas interreact. It seems to be independent of the pleasure principle. You can get very absorbed in it even if you don't especially like the look of the picture. It is fairly articulable too.
Heron's work is very involved with the push and pull of colours, how they seem to float in front of or withdraw behind one another, and can make a shape feel weighty or paper thin. He deploys their mutual magnetisms and infections: hues are transformed by their surroundings and neighbours, sometimes to the point of being quite disguised. Every area is kept active so that none, however large, relapses into being a mere background. This world isn't just a blast, it's busy.
When I say fairly articulable, that puts it mildy. In the hands of a vituoso Heron-critic, like Alan Gouk, a field of coloured blobs and scribbles can become startlingly active and dramatic. Here he is, writing about a painting from the early Eighties. We join the story half way through. "Just when it begins to seem that the pink runs the risk of bleaching out too pale, avert one's eyes for an instant and up it comes again, perfectly blushing at the discrete lemon wafer's sharply whispered suggestion, and a louder naughty importunity from a fluttering flaglet of deep red, almost too stark an intrusion, yet not..."
Yes, yes - this must be the way to do it. This catches the life of these pictures perfectly. Yet isn't it also bordering on absurdity, like the higher wine-criticism, the way such precision is given to what must be utter subjectivity. Can we take quite seriously this so-human drama. Are we really to see the pink as embarrassed?
A hard one. It seems to me that anyone who intently engages with a Heron picture is going to want to express themselves in this animated sort of way. The metaphors you choose will indeed be capricious and thus seem empty. But the sense that there is something definite that needs expressing is irresistible.
I think that touches on the draw of Heron's work - not its pursuit of pleasure, but its commitment to a mystery, which everyone with colour- vision must feel. The world of colour seems to us enormously important just because it is inexpressible, just because it is always lost in reproduction.
Tate Gallery, London, to 6 SeptReuse content