Bar of soap
Whitecaps, sea foam
Golf balls, baseballs, volleyballs, ping pong balls
Vanilla Ice cream
Shades of white: Ivory, milky, snowy, alabaster, lily-white, frosty, pearly, bone
Make every detail count
Colors are powerful descriptors, not fillers. Make sure that if you use a comparison or contrast to highlight a color, you choose the right one. Look at the setting and atmosphere you are working to create, then draw from the viewpoint character or narrator's history, education and past experiences to find the right fit.
A poor example:
After the light snowfall, our yard was a sheet of white, like clouds had fallen from the sky and blanketed the lawn.
What's wrong with this example?
At first this might appear as strong description, but the the more you think about the density and appearance of clouds, the more the image starts to resemble mist or fog than a thin crust of snow. Think carefully of not only the color, but the consistency of what your comparing to ensure a strong fit on all levels.
A strong example:
After the light snowfall, our yard was a sheet of white, like a tablecloth of freshly woven cotton waiting to receive the evening bounty.
Why is this example better?
This one conveys both a clean, fresh appearance and matches the thin coating implied by 'light snowfall'.