Researchers further hypothesized that if predation pressure is reduced, drab coloration would become less beneficial (since females prefer brightly colored mates). Based on this hypothesis, what prediction did the researchers test in this experiment?

The predation pressure increases mate

Explanation:

Since the observation of the scientist goes in order to increase the coloration in males, because of the predation pressure, and as a consequence the females are attracted by this colored mates.

It will be expected that the increase in pressure, it will increase the colored in skin, and this could end in an increase of the number of mates per male.