Dress code in the observation cells?

It depends upon the level of observation. If they are on strict mental health seclusion, they get only a suicide blanket. The psychiatrist visits mental health seclusion inmates daily (except weekends/holidays) and evaluates them to determine when they can get clothing and property back and what they can have at a given time.

The suicidal guys get a velcro-like jump suit that resembles something like a padded mini-dress.

The general mental health observation guys can wear their regular clothing.

We have mental health workers during the day that set the parameters for the suicide watches. But if you are the nurse working an off shift like I do, then the nurse sets the rules...everything from what they wear-jumpsuit only, underwear, blanket, type of mattress(if they get one), book etc...We also set the watch time. 15. 30. 45. 60. Min., and the type of watch-Suicide, behavioral, or medical. We take note of statements, behavior, history if we know one, eye contact etc... The length of time they stay on watch depends on mental health ( unless it's a medical watch). For example if they are put on 15 suicide watch when they are intoxicated and the next day when mental health follows up they are sober and ok they can move them right off watch. Otherwise they have to move up the chain of progression 15, then 30, etc.. Items they are allowed or removed can occur depending on that shift assessment.
Most often in my opinion it's not so frequently the ones that admit self harm that you have to worry about, but the ones who don't say anything.