There's a panel in Fireworks called Color Palette (Window > Color Palette) that has several different modes; the Selector mode offers a Color Picker-type layout with HLS, HSV, CMYK and RGB modes. Unlike Photoshop and Illustrator, its "grid vs. slider" interface is fixed, but it also provides individual sliders immediately beneath, which let you control each dimension independently. I think this was originally a third-party extension, and it doesn't quite feel as fully integrated as other default components, but it offers a lot of interesting functionality.
Fireworks' main color picker is a Swatches palette, but it also includes a System Color Picker option that lets you take advantage of your operating system's native color picker options, if they're available. On a Mac, this includes a variety of interface styles, including a Color Wheel, HSB Sliders, etc.
There's also Fireworks' native Color Mixer panel, which lacks visual feedback but is a handy way to adjust colors by dimension. It offers RGB, Hexadecimal, CMY, HSB, and Grayscale modes.