The correct type of selection in this scenario is disruptive selection. Disruptive selection occurs when individuals at both extremes of a trait distribution have a higher fitness than those with intermediate traits. In this case, brightly colored males and very dull males survive best, while males of intermediate coloring are less fit.
Therefore, the most likely statement about the proportion of males of intermediate coloring is that males of intermediate coloring make up a small part of the population.
So the correct response is:
Disruptive; males of intermediate coloring make up a small part of the population.