Isolation suits, also known as Anthropological Isolation suits, are technologically advanced type of clothing used by the Federation on pre-warp cultural observation or 'duck blind' missions. They are equipped with light refracting and sound dampening technology which function as a basic cloaking device rendering the user invisible to and sonically isolated from natives so not to contaminate there culture. (Star Trek: Insurrection)
The isolation suits are quite visible with properly configured sensor equipment which the base of operations for the mission will utilise to keep tabs on there personnel in the field.
When visible the suits are a reddish-orange colour and look like a low pressure suit which is no coincidence as the suits are sealed well enough to block out the noise of operatives in communications with the mission base from close by natives.