Considering the answers;
A) The difference among patches is due to natural selection. Blue individuals have higher reproductive success in some patches, white plants have higher success in some patches, and the two colors do equally well in some patches. B) The difference among patches is due to the founder effect. Some patches were founded by homozygous blue individuals, some patches by white individuals, and some patches by individuals carrying both alleles.
C) The difference among patches is due to genetic drift. Particulary if population size in a patch is small, one color or the other might be lost simply as a result of chance events, such as drought or herbivory.
I think all of the above explanations are plausible or possible.
