Blue
​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.
Faults:
*Light undercolor
*Discoloration of the fur - rusting or otherwise
*Silvering
*Light under colors


History:
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.


President's Notes:
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Genetics: aagg
a = black g = recessive blue

COLOR 
Agouti  
American blue agouti
Beige 
Black 
Blue
Buff 
Cinnamon
Champagne
Chocolate 
Chocolate agouti
Chocolate dove
Cocoa 
Coffee
Fawn
Mink
Pearl  
Platinum
Platinum agouti
Russian blue 
Russian blue agouti 
Russian cinnamon
Russian dove
Russian silver 
Russian silver agouti 
Silver Fawn  
UK Mink 
UK Lilac
Umber (Aussie Mink/brown) 

COLOR - C LOCUS 
Albino/Ivory 
Burmese 
Golden/Cream
Himalayan
Marten /Agouti Marten
Siamese Sable
Siamese

COLOR - MODIFIERS 
Marble 
Merle

FADING GENES 
Chinchilla 
Essex 
Frost 
Roan 
Variety-Breed Colors

COAT 
Bristle 
Hairless 
Harley 
Rex
Satin 
Silvermane
Standard
Velveteen 

MARKINGS
Bareback  
Berkshire
BEW (Black Eyed White)   
Blazed 
Capped
Dalmatian 
Dominant white spotting 
Downunder 
English Irish  
Irish 
Hooded
Masked 
Variegated
Odd-Eye 

BODY
Dwarf    
Dumbo 
Standard Ear
Manx