This is perhaps the most misunderstood gene of all, but
it is really very simple. A merle is a tri-colored dog or a sable-colored
dog with a dominant dilution gene and the dominant dilution gene is what
makes it become a merle. It is not recessive if it is present. The dog IS A
MERLE. This can be thought of more as a condition verses a color. There is
no way to get a merle unless you breed to a merle. You can think if it being
inherited independently of color. A Blue Merle is a tri-colored dog with a
dominant dilution gene.
A Sable Merle is a sable-colored dog with a dominant
dilution gene. The sable merle is a light stippled version
of sable, sometimes (as with blue merle) accompanied by blue or merled
(parti-colored) eyes. Blue eyes or merled eyes in a non-blue merle collie
are not disqualifications in the AKC standard although they are heavily
penalized. There are, however, plenty of blue-eyed or merled-eyed sable
merle collies who are AKC breed champions.