Strictly speaking the Koloroo colour scheme editor is not freeware so much as ‘careware’. Before you download it, you must agree to do something nice for someone. I kinda like it. They claim over 100 million color scheme possibilities, via the six main theories. That should be enough, eh?
Simply drag your cursor over the color wheel and watch as complete color schemes are generated and displayed in real-time. You can refine your color selection with the hue, saturation, and brightness sliders and choose from six different color matching methods.