Hummingbird feeders are red because that is the color that people think they should be. At one time, bird watchers thought that hummingbirds were attracted to red flowers. Since then, repeated studies have shown that there is not any single color that hummingbirds prefer. Instead, they are most attracted to the color of the local flower that is producing the best nectar. That changes as different flowers bloom, so one week your hummingbirds may prefer red, and a few days later, they may be more attracted to blue. Luckily, the hummingbirds see your feeder as a kind of flower, so once one of them discovers it, they will all be attracted, no matter what color it is.