Which property would you use to change the background color of an element?

The correct property to change the background color of an element in CSS is background-color. This property specifically targets the background of an element, allowing you to define its color using various formats such as hexadecimal values, RGB, RGBA, HSL, or named colors. When you apply background-color, it directly affects the visual appearance of the element's background, making it a fundamental part of styling web pages.

Understanding this property is crucial for web development, as background color plays a key role in layout aesthetics, user experience, and visual hierarchy. Other options listed, such as color, affect the text color rather than the background, while bg-color and fill-color are not valid CSS properties for backgrounds. This makes background-color the only suitable choice for altering the background of an element.