Appearance properties such as icon, font and colors:
the appearance properties are used to render the category, but also the items
that belong to that category. If a category has no color, font or icon of its
own, but it has a parent category with such a property, the parent's property
will be used. If an item belongs to multiple categories that each have a color
associated with it, a mixture of those colors will be used to render that
item.