Dogs do not see in the same way humans do, and they typically can perceive grey, blue and yellow. This is because dogs have only two types of cones in the retina for color reception, compared to the three in humans.
When a dog sees an object that is not yellow, blue or grey, it still perceives it as one of those three colors. For example, dogs see green objects as yellow and violet objects as blue. If an object in between yellow and blue on the color spectrum, a dog sees shades of grey. Colors are also less intense for dogs than humans.