Unfortunately photos often have a colour cast, perhaps a yellowy or bluish tint. Assuming your camera's settings are correct, this is not a fault with your camera's sensor, it is usually an accurate rendering of the colour of the available light. Different sources of light vary in colour.
Our eyes and brain adjust automatically to different coloured light so we tend not to see the tints. Old fashioned light bulbs and candles produce a yellow tint, and fluorescent tubes produce blue tinted light. There is even a difference between daylight on overcast and sunny days.
To remove this colour cast we need to make sure that white objects in your photo appear white. To do so we need to adjust the cameras white balance setting.
When the camera is set to auto white balance, it will automatically attempt to correct any colour cast, but this is never 100% accurate. Your camera may have other pre-set options for you to choose from such as cloudy, sunlight etc, and these may help. Try experimenting with these settings and see how they effect the image.
Another option is to use flash, even in daylight. The light of the flash will produce a more realistic appearance when problems with the white balance are particularly noticeable. You can use your flash in all lighting conditions, including brightly lit scenes.
The actual tone or tint of the colour cast is called the colour temperature. It is measured in degrees Kelvin. Some cameras let you choose a particular setting on the Kelvin scale as well as creating your own custom settings for particular lighting conditions.
Previously, film photographers used coloured filters to balance the light, but this wasn't very accurate. This approach is rarely used now because our digital cameras do a better job of producing a more accurate representation of light temperature.
You can also correct colour casts in post production. Camera Raw is an Adobe product and comes as a package with Photoshop. It includes a tool for changing your white balance so that the lighting looks natural. All you need is an object in your photo which you know is white. Select the white balance tool in Camera Raw, and click on the white object in the photo. The white balance will be automatically corrected for the whole picture.