First Night: Red, Donmar Warehouse, London

Dostoyevsky thought that if Christ were ever to return to Earth, we would crucify him all over again. Perhaps so, but it's a safe bet that, before we got round to that, hot fashion designers would be competing to recruit him as poster boy for some major new underwear campaign. High spirituality and low commerce are easy bedfellows these days. This was not the case, though in 1959, which is the date-line for Red, John Logan's new play set in the Manhattan studio of the great Abstract Expressionist artist, Mark Rothko.

In what Ken, his youthful new assistant, calls with some asperity "the flashiest mural commission since the Sistine Chapel", Rothko is hired, for a record-breaking $35,000 ($2m in today's terms), to provide a suite of painting as décor for the swanky Four Seasons Restaurant in the iconic new Seagram Building. Floating colour-fields of a rarefied purity, his layered, bluntly luminescent pictures use colour very much not as appetiser to pricey guzzling and swilling. Even a light snack of manna would feel a crude faux pas served as an accompaniment to contemplating these works. So, before at length reneging on the deal and returning the money, why did Rothko ever countenance this brush with Mammon? That's a question that becomes a bone of contention with the increasingly non-quiescent Ken.

Logan's two-hander is unveiled now in a brilliantly acted production by Michael Grandage who also pulls off, with superb élan and with huge help from the terrific set design by Christopher Oram, the tricky job of showing that the piece is a genuine "work" play as well as a resounding Oedipal clash of generations, differing attitudes to the significance of colour in art, and opposed views on how art should accommodate commerce. Usually in plays about artists, the most the leading actors ever have to do by way of impersonating picture-making as a manual task is execute, say, a tiny finishing stroke, such as is easy to fake.

In this event, though, the hard physical labour of creating a picture is forcefully enacted by the performers. In one amazing scene, they prime an entire canvas with buckets of blood-coloured red in a competitive frenzy that seems to subsume Rolf Harris at his friskiest with a pair of crazed axe murderers who have erupted in an orgy of unwise self-revelation. Frames are hammered into place; pictures are manhandled on and off Rothko's characteristic pulley system. We see the pictures with their black-on-red rectangles that hover in a peculiar mid-state between abattoir and transcendental trance – except for the one under particular discussion which remains visible only through the reactions of the characters as they gaze up at the theatrical "fourth wall".

For the kind of intense, but often bitchily witty debate that the play conducts, it would be hard to think of better casting. A shaven-headed, bespectacled Alfred Molina plays Rothko splendidly as an almost Asperger's-syndrome, tunnel-visioned visionary who is exorbitantly intent on turning his studio – and life – into a stage-managed theatrical set where the work can be seen in the best possible artificial light. As Ken, Eddie Redmayne gives further proof that he looks set to become the Mark Rylance of his generation. (Praise can't reach higher than that.) Here, he plays an initially meek assistant who is goaded into stingingly sarcastic arias of repudiation of Rothko and his values. Lean and whippety, Redmayne combines highly strung intelligence with the knack of seeming to have one layer of skin and one keenly apprehensive sense more than other people. So he's thrilling to watch as, heart clearly thumping and adrenal system in overdrive, his Ken inveighs against Rothko's over-investment in the expressive properties of colour (it's sentimental to fetishise black as tragic, he argues, when Van Gogh turned brilliant yellow into the vehicle of his mortal mania).

You can see from the fervent but catty dogmatism of Ken's own manner, as he gradually turns into the proponent of proto-Pop Art, that one day he will be the father-who-needs-to-be-killed to a youthful assistant of his own. It's another reminder of how easily the word "mentoring" can be distended to "mentally torturing". Recommended.