Dogs see more in the blue-green spectrum, not so much in the red spectrum. They see greens and yellows the best. Light receptors are composed of rods and cones. Rods allow you to see in the dark; cones allow you to see color. Rods and cones are fixed in size, so you can pack only so many in one eyeball. Dogs have more rods to see better in the dark, but sacrifice cones to make space for those rods.
Humans have reasonably good vision, but cones do not do the best job in seeing contrasts. Seeing in black and white allows one to see contrast much better. I believe it was in World War II that the military hired color-blind people (not people who lost only blues and greens- people who could only see in black and white- true color-blindness) to look at aerial photographs. Because of their ability to see contrasts, they were able to identify camouflage netting and such that a normal person couldn't see. Dogs can see stuff like that better.
There is also another way to separate vision qualities. Being able to see stuff that is still and being able to see stuff that is moving. Some brain damaged people have lost their vision and can't see a thing unless it is moving. When it moves, they can then describe what is there. I don't know for sure about this, but dogs seem to have better vision in the moving spectrum. Wildlife, too. Humans have this vision as well, but we don't really notice it.