The unexpected answer is: “No.”
In fact, their eyes are equipped to see many colors especially well, including red, orange, yellow, and some ultraviolet hues.
Why are hummingbird feeders almost exclusively red, then?
It’s actually all about the other pollinators, like bees and butterflies: They don’t see red very well, and therefore tend toward flowers of other colors. Thus, over time, our clever hummers learned that red flowers tended to carry more nectar!
So, if your feeder isn’t exclusively red, don’t worry! The hummingbirds should still come to check it out, and when they learn that it’s a rich food source, they’ll keep coming back.
Lastly, there is no need to put red nectar in the feeder to make it more visible. There is great controversy over whether or not red food coloring is unhealthy for these tiny little guys, so, just in case, it would be safest to stick with clear nectar – they’ll be attracted to the feeder just the same.