Bricks used in house building are usually red or tan in colour but using grey bricks can give your house a different, more contemporary look that will stand out.
Grey bricks can be made from clay, like traditional bricks, that has a high lime content giving them a white or yellowish colour, or from other materials.
Sand lime bricks contain, as the name suggests, a high percentage of sand (calcium silicate) with the remainder being lime. They tend to be more uniform in colour and texture since they are not fired in a kiln.
Concrete bricks, as the name suggests, are made by pouring concrete into a mould and can be formed in a wide variety of shapes and sizes.
Fly ash bricks consist of fly ash (a byproduct of burning coal) and cement. They are lighter than concrete bricks but the presence of fly ash can affect setting times and their overall strength.