Seed and boundary is a method of selecting part surfaces for a variety of purposes, in your case, for applying a color.
As Steven explained below, there are many types of objects in Proe, in general mimicking he real world. A real calculator is made up of an assembly of many parts, you typically would build each part in proe and assemble them together in a proe assembly. There are methods of top down design where you can build the parts within the assembly, but that's pretty advanced. best to master parts & assemblies separately first. 