Today, most mammals have dichromatic vision, meaning that they have two color receptors. Which color depends on which species you're asking. For example, the real reason bulls charge at matadors is the way they flaunt their flags--cattle CAN see color, but red does not register.
Other mammals, like dogs, have a different kind of color blindess:
Trichromacy, having three color receptors, is pretty common among the whole animal kingdom--for example, we have recently found the "red" gene in turtles--but when talking mammals, exclusive to only one order--the primates.
Regardless, reports have been popping up in recent years of humans possessing the gene that results in tetrachromacy, FOUR color receptors. As proof, just Google up Concetta Antico, an Australian artist who has been getting quite a popularity for letting her genetic condition inspire her paintings.
In Antico's case, tetrachromacy is a mutation that is not routine in the human genetic structure. But in this alternate scenario, tetrachromacy is a genetic normality among all primates and trichromacy among all non-primate mammals. Among humans, would this improve our night vision?