There are two types of gradients that Procreate offers; Radial and Liner
If you want to make a Radial Gradient:
- Make three consecutive inner circles of three different colors and then just apply a Gaussian Blur over the layer.
If you want to make a Liner Gradient:
- Create three colored strips one above the other, pick-up Gaussian Blur from the Effect Panel and then just hover the stylus over the stripes.