It is a myth that dogs can only see black and white. The misconception stems from the publisher of Dog Week Magazine, Will Judy, who claimed to be the first to say that dogs could only see single shades of color.
The primary difference between dog and human eyes as it relates to color perception is in the retina. "Dogs have more rods than cones in their retina, whereas people have more cones," according to an article published by the American Kennel Club. Humans are trichromatic, meaning they have three kinds of cones, while dogs are dichromatic, meaning they have two, missing the red and green cone. All this to say, dogs likely have similar vision to a human with red-green color blindness, according to research conducted by Jay Neitz, runner of the Neitz Color Vision Lab at the University of Washington. Dogs can still make out yellow and blue color combinations.
All in all, it is false that dogs can only see black and white. They don't have the same vision as most humans, but they can still see certain colors.
Can Dogs See Color? – American Kennel Club (akc.org)