BP has been trying since 2002 to get its shade of green (Pantone 348C to be precise) registered as a trade mark in Australia. The Trade Marks Office has just knocked it back again. Which begs the question – when can you register a colour as a trade mark?

It may seem a bit weird, but trade mark registration is indeed available for more than just words and logos – shapes, smells, sounds, movements and, yes, colours can also be registered. A trade mark is a symbol distinguishing a particular business or its product, and that can include all sorts of "things".

Of course, things other than words or pictures are much harder to register, simply because it's a lot more difficult for them to attain the necessary distinctiveness. But it's possible. For example, the windscreen company O'Brien has had its annoying jingle "Oh-Oh-Oh-O'Brien" registered as a sound mark. The classic Coke bottle outline is registered as a shape mark, as is the Toblerone triangle-shaped box.

Colour marks are relatively rare. Australia Post has both red and yellow registered for its services, Kraft has silver for its cream cheese, Christian Louboutin also has red for the soles of its women's shoes and a company called Fada has red too for the wax tips on its banana. Purple is also popular, being registered by both Cadburys for chocolate and Whiskas for cat food. Registration of a colour doesn't mean you own that colour or can prevent anyone else using it generally, but it does give protection in respect of the particular goods in respect of which you've registered it. Mind you, Cadburys tried long and hard to prevent Darrell Lea from selling chocolate in purple wrappers, and lost. So just how much protection you can really get is debatable.

BP is very attached to its green. We'd all readily identify that as its colour. However, Woolworths objected violently to the registration, and so far it's succeeded. Why would Woolies care? Possibly because it has spent a fortune in recent years rebranding to the same shade of green that BP uses, and perhaps because in the back of its mind there's a long term play relating to its close affiliation with Caltex in the petrol retailing space, and it wouldn't want to be shut out from branding all those petrol stations with the Woolies green apple. Just speculating, mind.

Practical advice? Applying for a colour trade mark is just as cheap as any other kind, so have a crack by all means if you've been using the same colour for 30 years or so. But on the enforcement side, don't expect miracles. Getting a colour registered isn't the pot of gold at the end of the rainbow (insert stupid pun here).