How can I adjust the white balance on my Coolpix A900?

Try doing a complete reset - this should return all settings to the factory options.

The only time I see WHITE BALANCE GREY is when your Picture Mode does not need it: When you are taking photos in B&W or monochrome or any mono color.

I may be WHITE BALANCE. If it is SET to FLASH and you are inside it may look YELLOW. Go the the MENU and see what the WHITE BALANCE is SET to. If it is AUTO then you MAY have something wrong with the camera. I cannot say it is the camera yet.

Unless you've changed the white balance in one of the PSAM modes, your camera should still be set to Auto White Balance. See the "White Balance" section beginning on page 53 of the manual: http://www.nikonusa.com/pdf/manuals/coolpix/CP8400_en.pdf

May I suggest you check your White Balance. It is best to always set the white balance manually before shooting. If it is in Auto then the white balance can change every shot. If you fix it it is best to set it before you shoot.

Incandescent lighting is yellow and shows up that way on photos. That's why digital cameras have white balance controls. Usually, auto white balance works ok but, sometimes you need to go into the settings and choose incandescent white balance to remove the yellow as you take the pics.

Sounds like your white balance is set to something other than "auto WB". Try a different setting.

You need to adjust the white balance setting.
This is on the shooting menu.

The options on the white balance presets are.
Flash, Cloudy, Daylight, Fluorescent, Incandescent
Fluorescent is what you are looking for.
Remember to change it back to auto for outdoor shoting.

can you preset the white balance using a white card or anything white can you shoot in raw format