Ready to Wear: People with light brown hair don’t actually look too bad in dark brown

You know that the January blues have well and truly established themselves when you find yourself, first thing on a Monday morning and with approximately 14 deadlines looming, watching re-runs of TV shows that you didn't much like in the first place.

And so, it's early January and here am I gawping morosely at repeats of Top Gear – yes, it's that bad – on Sky Planner when, safe in the knowledge that fashion never sleeps, I notice that, even off-Dr Who-duty, guest-of-the-week (and at that time, still Dr Who) David Tennant is wearing head-to-toe brown.

"Really," I think to myself. "It's bad enough when he's in character. He could have made an effort on Top Gear though and, while I'm at it, some general ground rules wouldn't go amiss." I'm talking to myself now; shouting at the telly – things must be bad...

Not to be deterred, though: "Rule number one: people with brown hair should never wear brown." That's Mr Tennant told, then.

In fact, as with most fashion dos and don'ts, some qualification is required. People with light brown hair don't actually look too bad in dark brown and, conversely, people with deep chestnut hair may like to risk fawn, say – the latter, in particular, is very Prada in flavour, although it has to be said that that requires a hefty dose of the kind of chic only very few possess.

The problem in question arises when a person's hair colour – any person's hair colour – perfectly matches their clothes. Even given a rather endearing revival of co-ordinated dress, Fifties-style, this is a step too far.

I ring a colleague (blonde).

"Should people with yellow hair wear yellow?" I ask her.

"Absolutely, definitely, certainly not," says she, neatly proving my point, although some might argue that nobody should wear yellow, whatever their colouring. Ever.

What about people with black hair, though? Surely they can wear black. Well, they can, of course, black still being the default non-colour of choice, but they do run the risk of Gothic overload – if they're pale-skinned – or simply disappearing entirely if they're dark. Hmmm.

The exception that proves the rule? Redheads. One in the eye for discrimination: in this instance any coppernobs out there have the edge. Witness Karen Elson in blood-red McQueen at the British Fashion Awards last month as one very lovely example. Strange to relate, any tone of red looks good on a redhead – from tangy orange-based hues to blue- and even pink-based ones. Whether their choice of this most dramatic of shades matches their tresses or indeed clashes with them, it only serves to add to any already considerable allure.