Dilute the sugar solution. Hummingbirds feed on nectar with about 20 percent sugar content, while bees feed on nectar with an average of 42 percent sugar content. If you make your own sugar solution, mix only 1 part sugar with 4 to 5 parts water.
Paint the feeder red or purchase a new feeder in red. Bees can't see the color red very well and usually don't feed on red flowers in nature. Additionally, the color attracts hummingbirds.
Fit a red bee guard on the hummingbird feeder to make it less visible to bees. According to Cornell University, yellow bee guards could attract bees instead of keeping them away. A bee guard is a little plastic screen that makes sugar solution inaccessible to insects.