A subcategory is always part of a top category. It can contain only words.
Just like a top category, a subcategory can be given a color. This color will be used by all contained words.
If a subcategory has no colour, or its colour has been removed, it uses the colour of its top category. See Editing items.
An administrator can, while editing a vocabulary, drag subcategories from one category to another. The dragged subcategories will not be copied; they will be moved. If you prefer a copy, first duplicate the subcategories. See Dragging.