I just realised that both the Egyptian god Osiris and the Indian god Krishna had blue skin color. How do you think that could be, considering that they were so far from each other. Another interesting fact is that both civilisations talked about the "Sun Gods", but also in the Americas.
Osiris sometimes is shown with blue skin, but it is more common to see depictions of him with green skin, which fits his qualities of a vegetation god associated with the renewal of life.
Ptah and Amun are often shown with blue skin. Some consider this to be an indication of their cosmic nature.
Sun gods are found in most civilisations. After all, the sun is one of the most obvious things of which we are aware (unless you live in Wales - joke!) and is of such clear importance, so it is not surprising that it is associated with divinity.