There are two different approaches you can use to apply a design to your Flex applications: styles and skins.
You can modify the appearance of any Flex components through the use of style properties, which can be used for setting the font size, background color, and many other predefined style properties. In this lesson, you will explore the use of styles, learn about style inheritance, and see several different ways to apply styles to your application.
The other option for customizing the look of a Flex application is by using skins, which are graphical elements (provided as files or drawn with ActionScript) that can be used to replace the default appearance of the varying states of a component. Although skinning is inherently more complex than applying styles, you will learn why you might need to do it, and how.