Electrical wires can be hot, neutral, or ground, and has a corresponding color ... Yes, you can connect red and black wires ...

A pretty typical diagram for the grounding system for a house is shown here, along with a few of the current carrying conductors commonly called live and neutral ... of the ground wire in ...

Green, green with yellow stripes and bare wires (wires without an insulated covering) in electrical boxes are “ground” wires ... you splice hot and neutral wires together.