In summer squash (Cucurbita pepo), fruit colour is determined by two independently assorting gene loci, $W$/$w$ and $Y$/$y$. The biochemical pathway responsible for this pigmentation is outlined in the diagram below:

A plant scientist crosses two double heterozygous plants ($WwYy$) to study inheritance patterns in the offspring.

Which of the following represents the expected phenotypic ratio of white : yellow : green fruits in the resulting $F_2$ generation?