Tom Sutcliffe: Only when colour on stage isn't an issue will we have made progress

I found myself wondering the other night whether a white actor will ever play Othello again. In the near future the answer to this question is obvious, I would have thought. Only last week the American playwright Bruce Norris withdrew permission for a German company to perform his play Clybourne Park, after learning that a white actress was going to play a black character.

The management's attempt to argue that the colour of the performer's skin was irrelevant and could be tweaked with make-up didn't impress him. And the Royal Shakespeare Company found itself under attack after it emerged that a production of the Chinese classic, The Orphan of Zhao, would include European actors playing Asian characters.

Artistic director Greg Doran's explanation that the same company were delivering three plays in total and that Asian actors would be playing non-Asians in other productions didn't appear to placate his critics, who included an East Asian actor who hadn't made it through the auditions. Given that degree of sensitivity about cross-racial casting, it doesn't seem likely that anyone would dare give the Moor to anyone but a black actor – though not impossible that an actor from the Maghreb might cut up rough.

My question wasn't really about probabilities, though, but about the propriety of such a thing ever happening – and it was prompted by watching Lolita Chakrabarti's play Red Velvet, which tells the story of the 19th-century actor Ira Aldridge, who astonished London theatre-goers when he replaced Edmund Kean in the role of Othello, after the great actor had fallen ill.

Chakrabarti's play – in which Adrian Lester gives a terrific performance as Aldridge – is in part an exploration of the weird tangle of assumptions we make about acting, and the ways in which racial identity gets knotted up within them.

The violent objections to Aldridge from the audience and contemporary critics were twofold; one, identity wasn't acting and devalued the transforming magic that Kean could achieve, and two, if Aldridge wasn't really acting, then when he laid hands on his Desdemona it was a real assault. The naturalism of Aldridge's style and his talent, Chakrabarti implied, aggravated that racist response.

It's a melancholy story and it presses home its point with a final coup de theatre, in which we see Aldridge whiting-up to play King Lear, a bleak moment of self-erasure. We might even be tempted at that moment to congratulate ourselves on how far we've come – since we know that Adrian Lester played Henry V several years ago to great critical acclaim, without a dab of panstick on his face.

But the truth is that there's still a considerable distance to go, and one of the things that tells you that is the current unthinkability of a white Othello – however radical the production. For the moment, for perfectly good reasons, colour-blind casting is actually only blind to colour in one direction. We'll know the issue is dead when no one gives a damn either way.