The HTML rendering engine can determine the style to use if conflicting styles are set on an element. For example, if an element has the color property set directly on it (DhElement.setColor), the color defined by the color property is used. However, if an element has a Style object on it (DhElement.setStyle) and that object has the color property set, that value is used. Failing to find a color or a style, the same process is used with the element's container (DhElement.getParent), and failing that, with the container of that container and so on.
The process continues up to the document. If the document doesn't have a color property set on it, the environment (either browser settings or some other environment settings) determines the color to use.
This process is called cascading styles because the properties cascade down the containment hierarchy. The underlying mechanism for DhStyle objects is called Cascading Style Sheets (CSS) by the W3C.