Ducks, like all birds, are not colorblind. Birds not only are not colorblind, but a large portion of them can see ultraviolet light. The only exception to seeing UV light are the nocturnal birds like owls.
Ducks and all birds can see reds, yellows and blues, just like humans do. The images are more vibrant than what a human would see though. This is due to an extra set of cones designed for seeing UV light or radiation. This increased the ducks sensitivity to light, known as tetra-chromatic. The ability to see UV light makes it easier for ducks to find food since many of their food sources put of UV light. This ability makes it easier for ducks to see at dusk and dawn, helping them avoid predators that are more active at midday.