Hi Bluesygirl,
This is most likely an auto white balance problem. Your hunch about experimenting in different lighting conditions is a good one. All digital cameras have problems adjusting their auto white balance, or color temperature. Some do better than others. The $5000 Leica M8 has lousy auto white balance according to many owners. But it has presets for different lighting conditions, such as daylight, cloudy, tungsten, flourescent, etc. It also has the ability to shoot in Raw, where you CAN alter the white balance after the fact without a problem. But this involves more time at the computer.
The iPhone camera does not have presets for white balance. So your only option is to attempt to post process the image in iPhoto or another imaging editing software. The temperature slider in iPhoto is the white balance adjustment. You can also play with levels and tint. The problem here is that a jpeg image has already thrown out a lot of the color data with compression, and adjustments after the fact are hit and miss.
It could be a software problem that will be improved upon, or even a hardware problem that iPhoneatlas speculates on without providing any evidence, but as an amateur photographer I can tell you this is very common among all digital cameras that don't have the option to preset the color temperature.
If you want to get into photography with a little point and shoot I would recommend a Fuji f30 ($300) or f20 (going for about $150 now) for super pics under varied lighting conditions, including the amazing ability to take them in extreme low light without a flash. You will be impressed.
But as far as the iPhone camera is concerned, it is what it is, a 2mp (I paid $500 7 years ago for my first digital, a 2mp model) fixed focus camera that only has auto white balance, a far from perfect solution to shooting in varied lighting conditions.
