You have two different problems rolled into one ... first the
*exposure* is getting thrown off by the large areas of white ... the
meter assumes medium-tones (gray) so that's why the whites look gray
... you would typically over expose by 1-2 stops to correct this, or
get the proper exposure by metering a gray card, if your camera allows
you to make manual adjustments.

Once you have the exposure part right then you have to worry about
balancing the color of the lighting, in digital terms this is typically
called "white balance" or similar.  Daylight has a different
temperature (and color) than artificial lights, for example.  If you're
using flash this part should be pretty easy.

I shoot for an arts magazine so I come up against this all the time. Shut
off all direct light as artwork can be shinny. Close the curtains. Digital
cameras are good about using the light that is available. Put the camera on
a tripod and use a cable release or a timer. Set the lens to the longest
tele to prevent warpage. Frame your shot as tight as possible. Set the
camera on auto and (RAW if you have it) and let it do what it wants. Shoot
it again with a sheet of white paper. Check your work to be sure you got an
image. If it looks noisy set for aperture wide open...there is no DOF on
flat work...and see if that helps.

Back at the computer set your white balance on the sheet of paper and set
your other shot to the same white balance. Use curves to adjust if
necessary.