Correct; if no one sees you use or take something outlined in red, it shouldn't cause any problems. Trying to sneak will let you know if anyone can see your character (it will fail, if so) and improve your chances of not being caught. An invisibility spell works even better.
Of course if you are deliberately doing something you need to sneak for, a quicksave wouldn't be a bad idea if you have not saved in awhile.
