When I was three years old, my proud Mum and Dad asked the local Maidstone portrait photographer to take a picture of their dear son. So it was that the snapper arrived at Bower Mount Road, and Robert was told to play with his Hornby train set on the floor of the lounge.

Following the custom of the time, the photographer colour-painted the resulting black-and-white photograph, which was duly delivered to my adoring parents. They were delighted. I was appalled. They admired the accuracy of my blond hair, my pink face, my blue eyes. I was outraged that the photographer had painted my toy locomotive blue - surely he knew that the livery of the London Midland and Scottish railway company was crimson. Did he care nothing for accuracy when it came to trains?

I remembered this while watching Apocalypse: The Second World War on the National Geographic channel this week. It's the latest colourised version of archive film, turning black and white into living colour for the benefit of contemporary audiences. But I was troubled by the National Geographic version of the Second World War.

In this week's episode, for example, the gunfire of warships seemed too crimson, and in last week's story of the fall of France, I felt that the colourisation was a bit on the cheap. There was archive film I hadn't seen before - especially of German troops taking the surrender of demoralised French soldiers - but while the trees were green, the Germans and their prisoners seemed pretty black and white. And a short clip of Hitler at home - taken by Eva Braun - was very odd.

I seem to remember that Braun used real colour stock when she photographed her Führer but this sequence was curiously muted, as if - and National Geographic will correct me if I'm wrong - the colourisers were dimming the real colour quality of the original Hitler pictures to match the newly coloured black-and-white footage in the rest of the film.

So are we distorting archive film by painting our Tommies in khaki uniforms, and turning grey trenches into brown mud?

On balance, I suspect not. You could argue that the archive black-and-white footage is itself a distortion - the real First World War was, after all, actually fought in colour, the blood was bright red, the trees, when there were any left, were actually green. All we are doing is redressing the inadequacies of 1914-18 film stock by providing it with the colour that it would have had if the cameramen were using today's technology.

But we all play tricks when we take pictures. From my days on the Sunday Express diary column - Peter McKay, please note - I learned how the paper's photographers took pictures of women. The stunners could pose how they wished. But women who were not as handsome as the photographer might have wished were asked to tilt their heads. The rule also sometimes applied to men. A tilted head meant that the viewer looked at the eyes rather than the face.

When I covered the Bosnian war, I took many of the pictures to accompany my own stories and usually - quite deliberately - in black and white, because in that terrible conflict I somehow wanted to bleed colour out of the world. The snow gave a monochrome horror to the Bosnian winters, and so many of the fighters and their civilian victims were so hungry that their faces were grey rather than pink.

But it's not just a question of colour. Sound was long ago added to silent archive footage to give verisimilitude to events, without any argument. First World War cavalry horses neigh; generals can be heard to talk and guns make a bang which the original cameramen must have heard but could not reproduce. And this falsification continues today, not by adding sound but by co-ordinating sound with pictures.

When I'm covering wars, for example, my vision and sound are not co-ordinated. An Israeli plane always bombs a target in silence. Only seconds later - depending on how close I am to the event - does the blast of sound reach me.

Every television network tidies the sound of war. In their reports, distant guns can be heard firing simultaneously with the flash from the barrel. It simply isn't worth the hassle of explaining the reality to the viewers, a BBC producer once told me. "Light travels faster than sound. So the BBC has to straighten it out!"

He was absolutely right. We have to organise what we film to fit the audience. War too. If only we could get steam locomotives the right colour.