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.