Recently a new coat colour gene has been discovered, among other colours, also producing a true blue gerbil.
Most likely this gene is the dilution gene d, already known in mice and rats.
This gene can dilute colours, because the pigment granules are not distributed properly which causes clumping. This will lead to dilution of all known colours. Basically, it will dilute all existing colours, most of them won't be very beautiful though. The darker colours can look good when they are diluted, like the black turning blue, the nutmeg might look funny, the burmese could be nice. And off course d will be able to make very light, almost white animals completely white.
The dilute black is called blue, leading to a dark grey/bluish colour, with slightly diluted eyes.

Picture by Vera Brueckmann

This mutation just popped up in a group of laboratory gerbils (grey agouti) at the university of Osnabrueck, Germany. Probably somewhere at the end of 1997. The first to pop up where the diluted grey agouti.
Well, they bred with these animals, and it turned out to be reproducible, so it is a new gene. So far, at the university, they have bred the blue (aaC-ddE-G-P- and aaC-ddE-ggP-) and the diluted golden agouti (A-C-ddE-G-P-).
Currently people from the Gerbil Genetics Group are outcrossing some dilute carrying animals, to confirm that this is indeed the dilute gene, and to make sure there are no other defects attached to this new mutation. And also to see how this gene interacts with the other, known, genes.

A dilute agouti pup (right) and an agouti pup.

A dilute grey agouti (l) and a dilute agouti.
Picture by Michael Mettler

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