It is the fear of every party guest, turning up in an outfit not suited to the dress code.
And unfortunately for Hillary Clinton, her slip up was witnessed by top government officials from across the globe.
Wearing a lime green shirt, the Secretary of State was placed in the middle of the foreign ministers - all dressed in crisp white shirts - for a G20 'family photo' in Los Cabos, Mexico.
But rather than adding a red face to the fashion faux pas, Clinton appeared to be tickled by her choice of outfit, laughing with her fellow leaders as the photographer snapped away.
And perhaps Clinton's colourful choice was intended to make an impact on the special occasion - she is in Mexico for the first G20 Ministers of Foreign Affairs informal meeting.
The gathering is an opportunity for the U.S. and other G20 members to discuss how to boost sustainable development, food security and the international economy, among other issues.
The Department of State said: 'This visit is an opportunity to reinforce close relations among nations and to identify common objectives and strategies to address global challenges and ensure global prosperity.'
Unfortunately, Clinton's wardrobe choice meant she looked far from 'at one' with her international counterparts.
For the photograph, Clinton was joined by leaders including the EU's foreign policy representative Baroness Catherine Ashton, Mexico's Patricia Espinose and South Africa's Maite Nkoana-Mashabane.
But it was an outfit not unexpected from the Secretary of State, known for her loud-coloured, boxy jacket and trouser suit combinations.
She raised eyebrows on a state visit to Barbados in June 2010 when she chose a gaudy bright orange trouser suit to meet the country's vice president.
Her questionable fashion choices led Project Runway's Tim Gunn to ask the following year: 'Why must she dress that way? I think she's confused about her gender. All these big, baggy menswear tailored pantsuits? I'm really serious.'
The Department of State was unable to identify a dress code which the Secretary of State had missed.
On Monday, the second day of the meeting in Los Cabos, Clinton signed an agreement with Mexico for developing oil and gas reservoirs that straddle the countries' boundaries.
It is the first deal of its kind signed by the U.S., and the leaders hope it will offer incentives for U.S. energy companies to work with the Mexican state oil company, Pemex, to develop resources.
Mexican President Felipe Calderon said: 'With this, we are setting aside the old fear that honestly exists among many Mexicans that Mexico’s oil could be extracted from the other side. Any joint reservoir will be jointly exploited.'
U.S. Secretary of the Interior Kenneth Salazar called the agreement an historic step that 'opens to door to previously off-limits areas in the Gulf of Mexico', Bloomberg reported;