Utena's base layer of clothing is this cropped black tank top and red shorts. I am mildly concerned about staining, but not enough to stop from dressing her in her clothing. (I suppose if her body acquires clothing stains badly and it bothered me, I could purchase a replacement body.)
I like that when she's just wearing this, she's dressed to beat the boys at basketball. :D This is what she is shown wearing in episodes where she plays basketball.