There are many different Shibori techniques that can be used to create very interesting patterns using dye. This is an ancient Japanese art that has many different techniques to achieve beautiful patterns on fabric.
To create an ombre effect, you must immerse different areas of your fabric in the dye for different periods of time. The fabric must be submerged one section at a time to create a fade from light to dark, or a fade of some sort. If you are unsatisfied with your ombre results, you can submerge your fabric for longer periods of time.