Answer: Most of the beetles will be brown because they have a higher likelihood of reaching reproductive age.
Natural selection is the process of selection by nature in which an individual organism exhibiting more favorable phenotypic characteristics has more chances of survival and reproduction in it's corresponding environment.
In the new environment, brown beetles can camouflage themselves from predators better than the green beetles and blue beetles can. This is because of the fact that brown color of beetle is a better phenotypic trait which favors the survival of brown beetles over green and blue color. Therefore, the survived brown beetles will reproduce and grow in number.
