This could be caused by many things, but the culprit may be the "White Balance" that the photograph was taken with. I'll try to briefly explain why.
Lighting from different sources burn at different "color temperatures" that affect the digital photos we take. Ordinary light bulbs=yellow/orange, florescent=blue/green, and others have white and varying shades. The human eye corrects this for us, but digital cameras use microprocessors to correct for different light sources; sometimes accurately, other times not. Pocket digital cameras have settings for white balance, but the problem is that most lighting is a blend of sources, from a glass window, to a desk lamp, to a camera flash. Higher-end cameras have custom settings that allow any given light condition to be corrected, but unfortunately the pocket digitals do not offer the same latitude.
In your case, although you used your camera flash as lighting, some stray light of the yellow/orange color coming off a room light or open widow could have crept in and the camera incorrectly adjusted the white balance. This may explain the increased richness of reds when the photo is created.
What to do about it? Software can correct it, if you have the time and dedication. Pocket digital cameras are limited in their ability to correct white balance, so upgrading to a camera with custom white balance correction will greatly decrease the occurrence. Shooting under controlled lighting will also help.
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John Robinson
http://www.armorartistry.com