re: Why blue is so rare in animals

Animals are usually colored to fit into their habitat. Ocean fish/sharks use counter shading (white on the bottom blends in well when looking upwards, and blue top shading works well while looking downwards).

On land there isn't really any blue to blend in with in the forest, hills, snow or plains. Most animals are that brownish/woody color.

Animals that use the vibrant blues you are referring to come with trade offs.
Evolutionary disadvantage - they are much more easily visible and spotted out to be prey.
Evolutionary Advantage - display of fertility, it is costly to stick out from your habitat as I mentioned earlier, but you are a badass individual of your species so your mates better recognize that you DGAF you gonna get the honeys.