Blue Rat Female

In the UK the NFRS standard for Blue (used by all British rat clubs) calls for a dark shade of steel blue without white undercoat. Breeders have managed to achieve this through selection, and kept the white undercolour to a minimum. Non-show quality blues are frequently lighter in shade, and may have varying amounts of white undercolour.

A lighter shade of blue is occasionally seen in the UK, and was bred in the early days as Powder Blue.These are less common nowadays and are classed as an Unstandardised variety.