Blue Engineering Brick Slips is a mottled blue/brown dependant on the angle you look at the brick from. This colouration is typical of the brick made in the staffordshire area using Etruria Marl.
This product has a smooth finish and square regular appearance akin to an engineering finish. It is relatively monotone in nature and works well with grey mortar colours.
If you are looking to create a below DPC brick installation this is typical of the engineering blues you often see. They are low water absorption and therefore very unlikely to fail due to frost.