Olivia Wilde wears white to a wedding - is it ever OK to embrace the fashion faux pas?

Dressing for a wedding can be a minefield. Too short, too revealing, too white?

It’s the last potential fashion faux-pas that is question on hundreds of soon-to-be guests' minds as we're coming up to peak wedding season.

The perennial debate for wedding guests everywhere was reignited over the weekend, as it appeared Olivia Wilde wore a white gown to her friend’s wedding.

The Don't Worry Darling director broke one of the number one wedding etiquette rules when slipped into a bridal-style white dress from Nili Lotan at the wedding of former Bachelor star Colton Underwood, 21, and political strategist and Wilde’s long-time friend Jordan C. Brown, 38.

Wilde, 39, posted a photo of herself at the Napa Valley wedding ceremony on her Instagram stories, captioning the image: "Wore a wedding dress to a wedding just so I could make a joke about it in my toast".

The actor and director is no stranger to throwing out the fashion rulebook for red carpet events, but a wedding is something else. She made it clear however, in her next Instagram post, that the newlyweds didn’t take issue with her wedding guest outfit.

"The grooms approved," she captioned the image of her hugging Underwood in the dress as Brown looks on.

But whilst the grooms approved on this occasion, it isn’t always that you’ll have such a forgiving wedding party. So is it ever ok to wear white to a wedding if its what the bride is wearing?

Can you ever wear white to a wedding?

It's one sartorial question that comes up time and time again on community websites such as Reddit and Netmums.

Under one woman's post on the parenting site, asking if the dress she was planning to wear at her friends wedding was too white, opinion was divided.

The outfit was a mid-length, one-shoulder white dress with black polka dots worn with a beige jacket and beige wedges, but many thought that white should be avoided at all costs.

“I wouldn't risk anything that white for a wedding,” one user wrote. “Stay well clear just to avoid upsetting the bride or her thinking it was done on purpose. Millions of other colours out there.”

“I would just never risk it,” another agreed. “If you have to ask "is this too white?" then it's too white to risk it.”

“Ladies off course it doesn't look bridal, that isn't the point. The rule is only the bride wear white at the wedding or am I missing the point?” another user commented.

However, others thought the dress was absolutely fine, not at all bridal and as long as the woman accessorises it with other colours it will be great to wear.

“This is nothing like a bridal or even a bridesmaids dress so I think it could pass,” one user suggested.

“The dress is totally fine,” another added. “I would have absolutely no idea why anyone would be upset by that dress. Accessorise with whatever you want to”.

How white is too white?

As a rule of thumb, if you have to ask, it's too white.

Unless the married couple-to-be explicitly state that their wedding will have a white theme, its best to avoid white at all costs. That also includes very pale creams and beiges, as in a photo, they will look close enough to white.

The etiquette guide is so that you don't end up wearing the same colour as a bride, which is typically white, but the rules also apply to wedding parties that don't opt for the obvious white.

Red, for example, is a go-to for brides in Chinese culture (if not for the main dress then for at least one of the many outfit changes), so wearing red as a wedding guest is a big no-no.

The best rule to go by? If you're unsure, just ask.

Watch: Where to buy affordable wedding guest dresses