Ok, the earth is quite big, so you'd have to be far away to be able to see the earth wholly at once. The colour correction is needed because of the fact that the earth rotates (aka day/night). Most earth imaging satellites orbit at like 500km, which is not nearly high enough to see all of the earth so the pictures have to be "stitched" together. Aka Photoshop. I don't think the apollo crew had colour cameras with them so that colour had to be added later. This will, of course, result in small differences. The photo's themselves are still original though.
