are all dogs color blind

Not all dogs are completely color blind in the sense of seeing only in black and white. Dogs are considered color blind compared to humans because their eyes have only two types of color receptors (cones), whereas humans have three. This means that dogs see the world mostly in combinations of blue and yellow, unable to distinguish reds and greens well. Essentially, their color vision is similar to human red-green color blindness, resulting in a limited color spectrum mostly in shades of blue and yellow. So, dogs are not entirely color blind but have a different, dichromatic color perception.