An implantable pulse generator includes a device housing containing pulse generator circuitry and a header connected to the device housing. The header includes a core assembly defining first and second lead bore cavities sized for receiving terminal pins of leads, first and second labels, and an outer layer. The first label is printed onto a surface of the core assembly proximate the first lead bore cavity and includes a first color. The second label is printed onto the surface of the core assembly proximate the second lead bore cavity and includes a second color different from the first color. The outer layer is overmolded over the core assembly so as to encapsulate the first and second labels and to allow access to the first and second lead bore cavities.