Not sure if there are any set standards for uniform but there are set standards for personel protective equipment in the UK, these standards are the same across Europe and result in a product being given an EN number. EN number apply not only to PPE but to a whole range of products. A full list of en standards can be found here;
www.standardsuk.com
High visibility jackets, EN 471, in order to comply with the standard the jackets must have a certain amount of reflective tape for night time visibility and flouresent material for day time visibility. Jackets are usually dayglow yellow in colour, dayglow orange jackets tend to be used where yellow jackets would be confused with other signals such as yellow flags used on railway lines or at motor sport events. Other colours can be added to the jackets, such as the green shoulders often seen on ambulance crew jackets or blue shoulders on police officers.
Jackets are divided into three classes dependant on how much visibility they offer, ambulance crew are issued with class 3 jackets, which offer the highest level of visibility. Class 3 jackets are required by UK law for anyone who may be required to work on a live road with a speed limit of 40mph or more.
Protective Helmets, EN443, this is the same standard used for fire fighting helmets.
Protective Footwear, EN345 and EN347, boots or shoes containing a protective toecap capable of resisting 200 joules. Many also have a protective midsole plate, the sole also provides basic protection from chemicals, oils and heat.
Protective Eyeware, EN166, avaliable either as standalone glasses/goggles or as a visor/eyeshield built into protective helmets.
Particulate Filter Masks, EN149, respiratory protection masks are divided into three classes often refered to as FFP1,FFP2 and FFP3 (filtering facepiece)dependent on the amount of protection offered against inhaled particles. FFP3 masks offer the highest level of protection and it is these that UK ambulances normally carry, FFP3 offers more protection than N95 masks, which are equivilant to FFP2.
Hope that helps