If someone was foolish in youth or pre-conversion, these days, it’s quite understandable. We should refrain from condemning the person until we get to know them. In general, Catholics should refrain from extreme and bizarre appearances out of a desire for humility. Those who do these things, at the time, demonstrate their wanting to stand out and make a statement of some sort, be it, “I’m a tough guy,” or “I’m proud to announce I’m LGBTQ.”
Most often, it actually reflects insecurity. “I WANT to be seen as a tough guy.” “I’m upset and confused about my sɛҳuąƖity. ACCEPT, no, CELEBRATE my chosen identity.”
In a few instances, these things are cultural, not any type of desire to stand out.
As Matthew says, hair can grow back, be cut, or restyled. Hair dye depending upon the type, can be washed out, wear off, out grown, or colored over in a more natural tone. Piercings usually close up. Tattoos can be covered with clothing. If not reasonable, can sometimes be removed or even re-tattooed to fade or blend more with natural skin tone. One can sometimes use makeup to cover them.
Many of these things would fall, imo, into the category of making reasonable adjustments out of respect for God, others, self. Unless the person is someone over whom we have considerable influence, it is best to MYOB.
In very extreme cases, like someone with a split tongue and tattoo of Satan on his face, or a person whose body art is immodest, blasphemous, the priest should handle the matter.