To create a gradient juice, start with layers of different colored juices or purees, ensuring each layer is well-separated. You can use syrups, fruit purees, or even natural food coloring to achieve the desired colors. Slowly pour each layer into a tall glass, starting with the darkest color at the bottom, and then gradually lightening towards the top. For a smoother transition, you can use a toothpick or a straw to gently mix the colors between layers.