The top and bottom shelves of the unit are either black or white and the middle shelves are glass.
This blogger started with white shelves and didn't make any changes:
|Via Style at Home|
The blogger from House of Hawks added paper to the top and bottom shelves to make them look a little nicer:
|Via House of Hawks|
The home owner from this Apartment Therapy house tour had a black unit and didn't change the shelves.
|Via Apartment Therapy|
The home featured on his Australian home blog had a black unit and either spray painted a mirror look into them or replaced the shelves with mirrors:
|Via Home Styling|
I think the last option is my favorite! A friend of ours recommended a local glass company to use for our shower wall in the new bathroom, so maybe I'll see if they can make us some mirrored shelves when we place our order with them.