The Modeler provides an auto-coloring feature in the modeler pad tab of its ribbon. The idea is that it’ll assign each namespace a color so you can easily spot in which namespace you are and from which namespace an entity comes from.
You don’t like the colors that were automatically assigned to your namespaces? You can set your own through the Background property of a namespace:
Since the namespace background uses WPF brushes, you can define a color, gradients (linear or radial) or even set an image as the namespace background!