White Balance. Get yourself a Lastolite Ezybalance grey card, and take a picture of it under the same conditions as the other photos. Iwould shootRAW, and use that photo to pick the white balance with the dropper in post processing. You can also use "Custom White Balance" on the camera if you shoot Jpeg. Short of a grey card, pick a white balance setting in post processing that is most appropriate. In Digital Photo Professional you can choose Daylight, Shade, Flash, Tungsten, etc. The difference can be stunning!