Is the color of the sky the same everywhere on earth?
Absolutely not. While the answers by casey and farrenthorpe correctly state that the blue color is due to Rayleigh scattering, the composition of the atmosphere varies considerably from place to place - and with different composition come different degrees of scattering, and different color / intensity. Typically regions of greater industrial activity will carry larger densities of particles which, in the presence of moisture in the air, will become scatterers. The wavelength dependence is a function of the size of the particles - so as the size changes, so will the color.

See my answer to the question Why is the sun brighter in Australia compared to parts of Asia. The same mechanism that makes the sun "brighter" also makes the sky "darker" (namely, less scatter).

This is true even on a nominally "clear" day - because there is always some particulate matter in the atmosphere. And the concentration of particulates really does vary with location on earth - see this image  as an example (from NASA).



The other point worth keeping in mind is altitude: the sky looks darker when you are at the top of a mountain, even if the composition of the atmosphere is the same. That is because there is "less atmosphere" to scatter. And of course, some places on Earth are (always) at a different altitude...