The majority of nursing schools have very specific "traditional" dress codes. Hair off the collar (whether short or pinned up), short, clean fingernails with no polish, single pair stud earrings (one per ear lobe), no facial or other visible piercings (may use flesh toned , sometimes clear " place holder" (sorry can't think of the right term now) is generally permitted), no visible tattoos, natural hair color (defined as close to what your base color would be--no "wild colors" or streaks such as blue, red, purple, green, etc.), no bracelets or jewelry, no rings (infection control and safety issue) though some programs permit a single band ring such as a wedding band style but it can be a pain with all the handwashing you are expected to do. No visible underwear (the classmate who elected to wear an animal print thong under their white uniform
pants was promptly sent home with an absence for the day)
When I was in school the dress code for classroom & clinical were similar with some exception (minimal jewelry was permitted as long as it wasn't a distraction...some people are more flashy than others and I mean that literally there were some who wore jewelery that literally flashed that was rather distracting when the lights were dimmed for videos & power points
), hair color was not as important when we were in the lecture only component of our coursework as long as it was neat & clean and not distracting. One young gal liked to wear very high pony tails and had very wavy hair that was somewhat wild. Depending on the day anyone sitting behind her couldn't view the lecture because her hair was in the way. She moved to the back or had to change her hairstyle.
Tatoos could be covered with long sleeves in most clinical settings except OR and other areas that required no outside clothing such as the special procedures unit, PACU, critical care, cath lab, etc. In these cases those with tatoos that would be visible were required by the clinical facility to wear a facility provided scrub jacket or gown. (Which wasn't a big deals since many of those areas were colder environments so the sleeves were appreciated!)