In this tutorial I will demonstrate how to use Noise and Blur tool create a beautiful background.
Create a new drawing using Java tool. From the menu select Effects -> Noise -> Render Color.
Use the blur tool under Effects > Blur > Box Blur to blur the effects of noise.
Set the blur amount to 50, try tweaking this value to adjust the fill effect in the next step.
Select the Fill tool from the tool window on the left. Choose desired colors and click on the canvas. Repeat this step with colors of your preference.