Something to keep in mind if you are going to dye the riser is that some dyes, especially water based dyes will raise the grain. To avoid this, wet the wood with a damp cloth, let dry, sand smooth again and repeat a couple times. By the time you add your intended dye the grain won't raise anymore.
And like others have said, you can dye curly maple and then sand it so that just the "curls" pop.