Given that she’s not exactly inconspicuous with her blue hair and she doesn’t seem to be bothering with a mask or cowl to try and conceal her identity, her powers must be incredibly effective at letting her get away with her crimes.
Well, we may not know too many plot details at this point, but I’d say that it’s safe to expect Janet Petty is a successful jewel thief as Null!
Still, it’s not like camo will help her blend into the streets of Central City.
In this image, she’s holding a crown so ornate that she almost certainly snagged it from a museum or private collection of a very wealthy person.