Blue is a simple recessive gene that dilutes the black pigment in the hair shaft. Crossing to silver lilac/mink tends to produce excessive silvering. Blue can have the tendency to rust or look patchy, easily, and should be selected for a clean and even appearance. Poor husbandry/nutrition can cause discoloration in the coat.
Description: Blue can be highly variable, and by determined selection, can be bred to dark and light extremes. There are three shades of blue that are accepted and shown. The darkest shade is called blue. The middle shade is called sky blue. And the lightest shade is called powder blue. These shades are all the same, genetically. The difference is merely which direction the line was selected.
Sky blue is the basic color produced if there has been no selection. Over generations, you can select a line to produce one extreme or another. Blue is created by selecting each generation to be as dark/slate as possible. And powder blue is achieved by selecting the lightest shade from each generation.
*Discoloration of the fur - rusting or otherwise
*Light under colors
Blue rats were discovered about the same time, in pet shops in the U.S. and the U.K. The first blue rat documented in the states was found by Sheryl Leisure in mid 1990. The variety was developed initially, in southern California. Interesting note: Sheryl Leisure also discovered the first merle rat.
Blue is also termed "American Blue" to differentiate from Russian blue. However Russian blue is already differentiated by "Russian," and adding to blue seems redundant. NFRS has labeled the dark shade as British blue.
a = black g = recessive blue
American blue agouti
Russian blue agouti
Russian silver agouti
Umber (Aussie Mink/brown)
COLOR - C LOCUS
Marten /Agouti Marten
COLOR - MODIFIERS
BEW (Black Eyed White)
Dominant white spotting