Blue as we think the most occurring color as 2/3 of Earth is covered of Blue ocean.
But do you really think it is most occurring color on Earth?
Well i wouldn't say that blue is particularly uncommon in nature.But we have never seen any blue tiger,Bat,Dog and squirrel.Even Blue whales aren't that blue.
isn't it strange?
Science tells us that the color of a body is the wavelength which it reflects e.g. yellow reflects yellow wavelength,similar with green and this is because the pigments on the skin of body.
But in case of Blue there is no naturally synthesized pigment(except in very small number of butterflies )
Even of many organisms which looks blue don't contain that pigment.
For example Blue morpho butterflies
These butterflies looks blue but these are not really blue.These are actually hologram.If we observer their structure microscopically it looks brown.
Then why it looks blue?
it is due to its structure when light enter inside the filament structure or scale's shape of wings different structures reflects different wavelengths which results into a shade while blue wave length become dominant because it is reflected from upper most structure that's the reason it looks like blue and when we tilt its wing it gives shades.
that's how we get this awesome iridescent blue.
if you don't believe you can experience it by spreading alcohol on its wings(Not promoting this kind of act).
This phenomenon is similar with blue jay feather.
Even your blue eyes are not blue due to blue pigment.
But as i mentioned above some of species DO MAKE BLUE PIGMENTS(very small number of species,we only know one )
and these are known as olive wings only single blue pigment butterfly we know about
So next time when you see blue Don't believe it is really blue.