The stitch pattern itself is almost garter stitch - so very subtle color changes would work, or color changes that occur slowly - that is, one color at the end of the yarn and changing to another color, like Noro yarns. Something like self-striping (where you go from color A to B to C back to A to B to C) wouldn't work nearly as well. The shawl isn't really meant to look striped, but mottled or shaded would look very good.