What went wrong?
Remember what I said earlier about cameras 'seeing' light in absolutes? It just happened again.
Fortunately, most cameras have what's called White Balance. Unless you change it, it's also set to 'Auto' - which does a fine job in certain situations - but not the one above obviously.
So how do I fix it?
If you have Photoshop, you can correct the problem somewhat using 'Curves>Auto' but it's really only half way there.
A better option would be to fix the problem within the camera.
Bad News: You can't do anything about the shots you've already taken*.
*Unless you shot in RAW Mode
Good News: It's a better fix than Photoshop.
How?
Take a picture of something that's supposed to be white. That something should also be very close to what you're going to take a picture of. Technically it should be 18% gray, but white is easier to find and it doesn't make a huge amount of difference. You might find it helpful to put the camera in manual focus mode so it doesn't have to try and lock onto anything - it will just take the picture.
Find how to how to set 'Custom White Balance' with your particular camera. Use the picture like the one taken above for calibration.
Take another picture with an actual subject in it. It should now look like this:
