The processing selectivity in the flanker task has been shown to depend on the ratio of congruent trials to incongruent trials in a task (Gratton, Coles, & Donchin, 1992). If congruent trials are more frequent than incongruent ones, the flankers are more attended and, consequently, the flanker congruency effect is increased. Recent results suggest that participants can even allocate attention on the fly to the flankers-that is, in a highly flexible way after stimulus onset-depending on the frequency of incongruent trials on a certain stimulus location. Because location plays a unique role in stimulus selection, we investigated in two experiments whether selectivity can also be adjusted on the fly depending on stimulus color. The results demonstrate that color can be used for such an adjustment, but only if the association between color and frequency has be enpreviously learned under blocked conditions.