Hunter paramedic Natasha Whiteley says she felt attacked when NSW Ambulance management made her change her hair colour.
Colleagues will colour their hair on Thursday to show solidarity with Ms Whiteley, after she was disciplined for dyeing her hair red.
Ms Whiteley, an HSU (Health Services Union) delegate, said management "forced me to change my hair colour to a more professional - in their words - natural colour".
This was despite the fact her hair was naturally red.
"I got an ultimatum of do not return to work unless your hair is a normal colour," Ms Whiteley said.
"I felt attacked and like it was a complete waste of time.
"I had to bleach my hair, which destroyed it, and I chopped it all off. It's now really short."
She said it "shouldn't matter what colour my hair is".
"It has nothing to do with our work. We go to people in cardiac arrest and I don't think they would care if my hair was rainbow, blue or hot pink."
Ms Whiteley had been a paramedic for three years, a nurse for 10 years and had five years of medical training.
She added that paramedics were "being pulled up for having more than one earring, a nose piercing, for the colour of their socks, or for not having shaved that morning".
"I've just been the most vocal about it, but it's a widely felt issue."
She said management had previously opposed tattoos, but that had "very recently changed".
Her colleagues at Medowie Ambulance Station were "standing by her", the HSU said.
Paramedics in the Hunter zone from Nelson Bay to Belmont will take part in the protest.
Ms Whiteley dyed her hair red in September and was reprimanded under the NSW Ambulance uniform policy.
HSU secretary Gerard Hayes said it made no sense for the ambulance service to be concerned about the colour of paramedics' hair.
"They're treating the ambulance code like it's 1970," Mr Hayes said.
"Paramedics are reflective of their community. In this day and age, people colour their hair and have different forms of haircuts.
"Why would a paramedic be any different to those they're looking after?"
A NSW Ambulance spokesperson said its uniform policy was "currently due for review".
"The changing views of the community and workforce will be considered as part of that review," it said.
It added that the review would ensure "the appropriate professional standards expected of registered healthcare practitioners".
"NSW Ambulance is reaching out to contact the paramedic involved."
Paramedics will colour their hair together on their shift to show concern that the ambulance uniform policy was being used "in a draconian manner".
Mr Hayes said the disciplinary action was "completely overcooked".
"But if they want a blue, they will absolutely get one. The anger of paramedics is red hot," he quipped.
Mr Hayes will support the action by dyeing his hair blue.
"This action should not be necessary, but we are determined to show collective strength against petty management nonsense," he said.
The HSU stated that NSW Ambulance had "one of the strictest uniform policies in the state".
"Many members are not impressed," it said on social media.
Management was using "outdated, conservative ideas of what a paramedic, worker or woman should look like".
The HSU statement added that the NSW Ambulance executive "preaches inclusion and self-expression".
However, they "rarely practise what they preach".
It said the uniform policy was "unbelievably inconsistent in application".
A NSW Ambulance Instagram post on July 16 showed a female paramedic at the Western Sydney Careers Expo with the same hair colour as the disciplined woman.
"Clearly, the service doesn't mind dyed hair that much. It's time for the policy to change," the HSU statement said.
