Purple snail pic

I wonder if the blues are mating with the chestnuts to create this color?

Its a normal color variation, its likely the chestnut carries the gene for it, although the blue could as well. You did not "create" the color, there are TONS of color possibilities in bridgesii, some are just more recessive than others.
 
at my petsmart i finaly saw blue brigs and i like yelled omg but when i looked they weren't green -.-
 
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