A two-tone dress marketed as being “bang on trend” has lived up to its billing — by sparking a global debate on Twitter over what colour it is.

The figure-hugging frock has divided opinion across social media, with some people viewing it as black and blue and others claiming to see white and gold.

A picture of the knee-length dress is reported to have first been posted online by Caitlin McNeill (21) from Scotland.

Although Birmingham-based Roman Originals describe the dress as being royal blue and black, friends of Ms McNeill had noticed several different colours in the garment.

The on-line furore surrounding the dress has seen the hashtag #TheDress trending on Twitter, alongside #TheDressIsWhiteAndGold and #TheDressBlueAndBlack and the much less popular #TheDressIsBlue.

Ms McNeill told the BBC she posted the picture on a photo-sharing site after her friend’s mother wore the dress at a wedding.

The aspiring musician told BBC Radio 1’s Newsbeat: “Two of my very good friends were getting married and they asked me to put together a band to come and play at the wedding. This was a wedding on the tiny island that we come from on the west coast of Scotland called Colonsay and about 100 people were there.

“A week beforehand the bride had been sent by her mother a picture of the dress she was going to wear and when the bride showed her fiance, they disagreed about what colour it was.

“She was like, ‘It’s white and gold’ and he said, ‘It’s blue and black’.

"So they posted it on Facebook to try and see what their friends were saying but that caused carnage on Facebook."

Celebrities who have tweeted about the dress include reality TV star Kim Kardashian and her rapper husband Kanye West.

A spokesman for Roman Originals, which is based in Erdington, Birmingham, said it had put all available stock of the dress in to its online store and its network of shops.

The in-demand outfit briefly sold out and talks are under way to assess whether its production levels will be upped.

The spokesman said the dress was also available in three other colours, including a red and black version.

“It’s black and blue but we’re definitely looking into a white and gold version,” the spokesman added.

One possible explanation being reported as to why people are seeing different colours may be down to an optical illusion, stemming from how the human brain processes colours.

The brain’s perception can be thrown by the colours of nearby objects, and their reflected light falling on the object in focus — in this case the dress.

However, whatever the science behind the colour mismatch, the social media debate shows no sign of abating.

Professor Stephen Westland, chair of colour science and technology at the University of Leeds, said the way people see colours varies hugely.

He said: “One in 12 men is colour blind. But what people don’t know is that even if the rest of us are not colour blind we don’t always see colour in the same way.

“The surprising thing is that this doesn’t happen more often.

“People think if they take a photo of something, people will see the same thing but of course that is not true.”

Prof Westland said that the “strange” lighting in the picture had probably contributed to the confusion.

He said: “If it hadn’t been taken under very strange lighting this probably wouldn’t have happened because if you look at the manufacturer’s picture, it is indisputably blue and black.

“It’s quite confusing because I’m not always clear whether people are even looking at the same picture half the time as there are now different versions on the internet.

“But that isn’t the answer because people are often looking at the same screen and seeing different colours.”

Prof Westland explained that the confusion could stem from how we name colours, as there are often blurred lines between how we interpret what colour something is.

But, he said, this is an extreme case as “there is a huge difference between black and gold, blue and white”.

He said: “It is possible that people could literally be seeing different colours but it’s impossible to know what is in someone’s head.”

PA