Final answer:
The two black wires are connected to the 4-way flat connector wires using yellow colored butt connectors, with color-coding useful for identifying different types of wires such as live/hot, neutral, and ground.
Step-by-step explanation:
The right-side black wire and the left-side black wire are attached to the 4-way flat connector wires, by using two yellow colored butt connectors. In the context of electrical wiring and the use of a three-hole outlet, the color-coding of insulation is important for identifying different types of wires such as live/hot, neutral, and ground wires. However, these color codes can vary depending on the region. It is typically understood that live/hot wires might be colored brown, red, black, blue, or grey, whereas neutral wires could be blue, black, or white. Ground wires, on the other hand, are often green, yellow, or may even be a bare wire without insulation. For the safe installation of electrical systems, it is essential to be aware of the color code standards in your specific area.