Is Darker More Effective? The Effect of Package Color Lightness on Consumer Judgment of Product Efficacy

ABSTRACT Product efficacy is a crucial consideration in consumer's purchasing decisions. However, assessing product efficacy is often challenging for consumers owing to its unobservability, thus prompting them to depend on observable cues for evaluation. This research examines the impact of a visually perceptible cue—package color lightness—on consumer judgment of product efficacy. Using a field study and three experimental studies, we demonstrate that consumers perceive products with darker‐colored (vs. lighter‐colored) packages as having a higher concentration of ingredients, leading them to judge the products as more (or less) effective. Nonetheless, this perception also leads to an associated concern regarding side effects. We further uncover that consumption goals—whether prioritizing effectiveness or safety—moderate consumer preference for products in darker‐colored versus lighter‐colored packaging. These findings enrich existing literature on color and product efficacy judgment and provide insights for marketers focused on efficacious products and visual design.