Good evening Cheryl! Here are my updated explanations for this question.

All points along the same colour are at the same potential simply because there is no resistor blocking the way along the same colour paths. All the points along the same colour wires are at the same potential. As such, the potential at Y and Z are the same, and similarly, the potential at C and D are the same. Note, however, that the potential at Y and C are not the same all because of the resistor.

Voltage across the resistor (between C and Y) is defined to be the difference in potential levels across the resistor. So for example, if point Y is at a potential level of 2.5 V (and so do W, X and Z), point C must lie at a potential level of 1.0 V (and so do A, B and D).

The highest potential level starts fresh from the positive end of the terminal (at 3.0 V) before dropping along the 1.0 ohm resistor by 1.5 V to a potential level of 1.0 V along WXYZ and dropping further by 1.5 V across the resistors in parallel to a potential level of 0 V along ABCD. Potentials return to the negative end at a level of 0 V and then regenerates again at the positive end fresh at 3.0 V.