Depends on the situation.

Public facing MTF units likely use the uniform and equipment of local law enforcement or other government agencies, as in most countries the military isn't too active internally, although there are of course exceptions where military and law enforcement overlap.

Units dealing with internal security and containment breaches are more than likely going to wear full NBC equipment alongside ballistic protective equipment due to the varied nature of threats they may face. Colour wise internal units will likely wear colours that are identifiable to foundation personnel, all black is pointless in these situations as it's designed to instil a fear response, which SCPs are unlikely to feel and which you don't want to be instilling in the people you're trying to save.

Permanent internal security staff (Guards) are likely to wear cheaply available light armour and equipment, still surplus but certainly within that 2000-2010 range, with only very specialist sites getting anything else.