Question : Apply gradient to cuved shape, like an 'S'

I've been looking around for a method in either Illustrator or Photoshop to have a gradient follow the path of the capital letter S, but haven't found anything yet.  For example, with a red-to-blue gradient, the S would be red at the top end, and the gradient would follow the curve down and around so that the S is blue at the bottom end.

Any convenient way to do that?  Seems as though that would be a fairly common thing.

Answer : Apply gradient to cuved shape, like an 'S'

Make a red box about the thickness of the S shape.
Make a blue box of same size.

Select both boxes.
With the Blend tool click on one anchor point on the red box and same anchor point on the blue box. Now you have a blend.

Make an S shaped path near by. Select both the blend and the new S path.

Go to: Object > Blend > Replace Spine