Because BeOS has a sophisticated messaging system behind the scenes, both developers and users can do some pretty cool tricks that just aren’t possible (or that are very difficult to do) on other operating systems. For example, take a look at Marco Nellisen’s ColorFontSelector, which is capable of broadcasting messages to all kinds of applications (the color picker in some BeOS graphics apps can do this as well).
If you drag a color out of the color picker palette and onto the Desktop, the Desktop changes to that color. If you drag a color onto DeskCalc, the calculator takes on that color. If you drag the color into your favorite text or HTML editor, the color’s hex value will be inserted into the editor. None of these applications were designed to work specifically with the color picker — the magic of BMessages makes it possible for any app to communicate with any other app easily.