All three waterproof laser paper stock sizes - 8 1/2" x 11", 12" x 18", and 14.33" x 20.5" - are available in standard white or any of the following colors:
Colored waterproof laser paper sheets are available in the 4.7 mil thickness only.  White is also available in 3.7 mil, 4.7 mil, 7.7 mil, 10.7 mil and 13.7 mil thicknesses.