From the moon, the earth is just a blue and white ball

- albeit a very beautiful one.

Yes, many people are aware of what you say having seen pictures such as Earthrise:
http://www.abc.net.au/science/moon/earthrise.htm

That's presumably why the myth was amended to specify the Great Wall as the only man-made object visible from space after the Apollo missions (at a guess).

I wonder how many myths have gone through a similar re-write to survive in the face of new evidence and new common experiences?