British blue represents the darkest end of the blue spectrum, and powder blue is the contrast to that. It’s not a variety that is commonly bred as mating to a British blue (or black from British blue lines) would be a huge step backwards for the powder blue as it would darken the top colour and decrease or remove the pale undercoat. Blues from platinum lines tend to be powder blue rather than any of the darker shades, and they would probably be a good variety to run alongside powder blues.
There are a fair number of British blues shown that have pale undercoats, and/or pale top colours – really, these rats probably make life difficult for powder blues, when the USPs of the powders are only seen on the bench as faults for British blues.
Genetics: Non-agouti with the blue gene, selected for pale colour (aadd)
NFRS standard: To be a pale dove blue colour, with pale silver base fur. Pale silver underbelly. Should be distinctively different to that of the slate colour of the blue rat. Colour to be as even as possible, devoid of dinginess, white hairs or patches. Foot colour to match top. Eyes Black or Ruby.