Adobe Illustrator. Use Gradients. Y
Sorry I clicked on the return by mistake.
You can use the curvature tool or any other shape tools to create theShapes.
Use gradients on the shapes. Create Your or use the one that come with ilustrator.
You can also use the blob brush and brush the shapes.
Lots of ways!!!
Blob brush with a gradient....
You could take a look at gradients on strokes. Like this:
Move the points into the correct position: