Young people appear to have relatively little motivation to participate in flu-vaccination programs. This study assessed the effectiveness of online banners in efforts to persuade young people to get vaccinated. Specifically, a 2 x 3 between-subjects factorial design was used to examine the effects of message framing (gain vs loss) and color configuration (white text on a red background, black text on a yellow background, and white text on a blue background) on 180 college students' perceptions of the persuasiveness of flu-vaccination promotional banners. Each participant completed a four-item questionnaire, and the results of an analysis of variance showed that persuasiveness scores were higher among participants exposed to a loss-framed than to a gain-framed message, but only when the loss-framed message was presented in white text on a red background. The theoretical and practical implications of manipulating these two factors in the development of effective health-promotion materials are discussed.