What is an example of improper vehicle equipment related to rear lamps?

Using white lights on the rear of a vehicle is indeed an example of improper vehicle equipment related to rear lamps. In most jurisdictions, including Iowa, rear lamps are required to emit red light, which is standard for indicating the presence and size of a vehicle to drivers behind it. White lights are typically used for front illumination; having them on the rear could confuse other drivers about the vehicle's intentions or position, as it deviates from established traffic safety norms.

The other options do describe issues related to rear lamps but are not the explicit example of improper equipment like the use of white lights on the rear. For instance, while failure to have any rear lamps is a significant safety violation, it does not pertain to the use of colors. Similarly, rear lamps that emit different colors may also indicate improper equipment, but the use of white lights is more specifically regulated and represents a common misstep in vehicle lighting configurations. Having functional rear lamps but using non-standard bulbs generally pertains to the specifications of the equipment rather than color use, but it does not inherently convey the same level of safety concern as the use of white lights.