Not to be a pedant, but--
The effect is called barrel distortion, straight lines bow outward. This is the result of cost compromises of lens design, most often seen in wide-angle lenses or the wide settings of inexpensive zoom lenses. This shows up in "macro" pictures because the "macro" setting almost always defaults to a lens's widest-angle focal length.
The opposite effect, with straight lines bowing inward, is called pincushion distortion and usually associated with long focal lengths.
As Norm notes, placing straight lines as closely as possible to the horizontal center of the fame is the only way to reduce the effect without investing in different photographic equipment.
Spherical aberration is seen as slight "fuzziness" surrounding sharp points of focus. This is the result of lens design which does not adequately focus off-axis light rays.
The color cast problem requires explanation of how light suffuses the interior of your camera. Proper remediation is not easily, and requires photographic techniques more sophisticated than simple gamma correction. If you really want to avoid it, the only solution is to photograph with a white background in the first place. You can add a color background later, but the techniques are far beyond explanation here. This very problem, and its ultimate solution, delayed publication of "Police Lugers" for almost a year.
--Dwight
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