First of all, hummingbirds don’t live on nectar alone: insects are the bulk of their diet.
When looking for nectar, while they are indeed attracted to the colors red and orange, but they actually drink nectar from a variety of flowers that have a specific sugar content (10-25%).
Red hummingbird feeders simply help them identify a potential food source from a distance. We are just beginning to learn about their sense of smell. This recent study found they do sense chemical cues from some insects. (SOURCE: empressofdirt.net)