The functionality you’re looking for (Multicolored blend texturing) isn’t in the latest release of Fiber (2.03). I’m working on updating the script to version 3.0, and this will be one of the main new features. Things are really commong along, especially with the help of eeshlo. And I would agree that polygonal hair (maybe uv-mapped with a soft alpha map for a soft appearance) is much more realistic than particle hair, and also easier to work with as long as your computer doesn’t grind to a halt.
Maybe what you want to do is use Fiber 2.03 and then vertex-paint the resulting fibers to acheive the pattern you want.