Macromedia - Keep Your Movies Lean By Reusing Symbols (Flash 5/MX)
When working in Flash, don't get in the habit of re-creating shapes whenever you need a variant of a current graphical symbol. Instead, try to recycle the element whenever possible, thereby keeping the file size as small as possible. Remember that you can use the symbol as many times as you like--even across movies. If you need a different look for the item, simply alter the alpha, tint, and advance properties.