This image was generated by using Blender:
1. [Shift + A] to create a new curve point.
2. Make sure to click the [3D] button.
3. [E] to extrude.
4. Type [A], [V], and [A] to smooth the curve.
I have included the [test.blend] file in the zip file.
Go to Brush Options, and click [Predefined]. Click [Import] to import the image above.
Spacing needs to be activated, and the value should be between 0.1 to 0.2.
Create a new document, and fill it with black. Create a new layer.
Paint with a newly created brush like this.
Right click the layer to add a new style, and add a new Gradient Overlay like this.
Try adding more layers and applying different gradient colors.
This is the end of the tutorial. 🙂