The scenario described involves brightly colored males and very dull males surviving best, which suggests that there is an advantage to both extremes of coloration, while males of intermediate coloring do not perform as well. This pattern is characteristic of disruptive selection, where individuals at both extremes of a trait are favored over those with intermediate traits.
Therefore, the correct answer is:
B. Disruptive; males of intermediate coloring make up a small part of the population.