Is grey a judo belt color?

The belt order goes as follows:

White (Single Wide)

Yellow

Orange

Green

Blue

Purple

Brown

Black (1-5th Dan)

Red and White (6th-8th Dan, Most Still Wear Black.)

Solid Red (9-10th Dan)

Double Wide White Belt (12th Dan, has never been awarded. Perfection has to be attained before receiving this belt, and perfection is not possible. The Kodokan, and other judo organizations have the power to award this but never have.)