In a tropical forest some leaves are dark green and some are light green. in a population of caterpillars, homozygous dominant dark green caterpillars thrive eating the dark green foliage, while homozygous recessive light green caterpillars thrive eating light green foliage. however, heterozygous caterpillars of an intermediate color green are easily seen by birds and eaten, thus their numbers are far less than the dominants or recessives. this is an example of selection.

This is an example of "Disruptive selection".

Explanation:

Disruptive selection occurs when selective pressure favor homozygous. In equilibrium, the two alleles might be present or one of them might be lost. If an environment has two extremes, then in these environments, both alleles are presented in homozygous.  

The disruptive selection causes an increase in the two types of extreme phenotypes over the intermediate forms. Limits between one extreme and the other are frequently very sharped. Individuals belonging to one phenotype can not live in the same area as individuals belonging to the other phenotype, due to the traits differences between them, competition, or predation.

Populations show two favored extreme phenotypes and a few individuals in the middle. Individuals who survive best are the ones who have traits on the extremes forms.  Individuals in the middle are not successful at survival or reproduction.

Color is very important when it comes to camouflage. Dark green caterpillars that live in dark foliage and light green caterpillars that live in light foliage can hide from predators more effectively and will live the longest. Intermediate colored green caterpillars that don't camouflage or blend into either will be eaten more quickly.