What factor primarily influences the color of the malt?

The primary factor that influences the color of the malt is indeed the duration and temperature of kilning. During the kilning process, malted barley is dried and heated, which causes a series of Maillard reactions and caramelization. These chemical reactions are responsible for the development of various colors and flavors in the malt. Higher temperatures and longer kilning times generally lead to darker malts due to these reactions, while lower temperatures and shorter times produce lighter malts.

The variety of barley used does have some impact on flavor profiles and potentially some color characteristics, but it is not the main determining factor for malt color. Fermentation time primarily affects the flavor and aroma of the beer rather than the malt color, as it occurs after malting and kilning. Water pH levels can influence some aspects of brewing, such as extraction efficiency and flavor, but they do not directly affect malt color during the kilning process. Thus, the correct answer highlights that the kilning process is the crucial step that establishes the final color of the malt used in brewing.