Merle is a genetic pattern that can be in a dog's coat. Merle comes in different colors and patterns and can affect all coat colors. The merle gene creates mottled patches of color in a solid or piebald coat, blue or odd-colored eyes, and can affect skin pigment as well. There are two general types of colored patches that will appear in a merle coat: liver (red merle) and black (blue merle). They are by far the most desirable pattern.

“Blue” in reference to a dog's coat is any variation of a silvery-grey color, often having a distinctly icy sheen. It's not really a “blue” tint that's comparable to navy or sky blue, but it's most certainly a cooler color that makes this hue stand out from typical gray and black coats.

Isabella or a Lilac French bulldog has a noticeable lilac hue of the coat. It occurs due to the same dilution gene that causes a blue hue of hair. If you would ask us to describe this coat color, we can say it a pale greyish-brown coat.

A French Bulldog is considered black if the coat color is solid without any signs of brindle, which is rare. Even if a puppy appears black, that might not be the case. A truly black French Bulldog has an unique DNA of a/a.