Everybody loves hummingbirds, so the last thing we want to do is to harm them. Do not use red-dye solution or add red food coloring in your hummingbird feeders.

Toxic Chemicals
Commercial nectars contain a petroleum-based dye, Red Dye #40. Although this dye is approved by the FDA in the United States, there is enough uncertainty about the safety of Red Dye #40 that it is banned in Austria, Belgium, Denmark, France, Germany, Sweden, and Switzerland. 

When Shimmer? When Not?
When you look at an animal, it's usually easy to tell what color it is, but hummingbirds can fool us! Sometimes the hummer's throat feathers, called the gorget, shimmers with color. But other times it looks dark.

For a long time, scientists didn't know what made the gorgets of many male hummingbirds seem to change. But now they have an idea, thanks to special microscopes that allowed them to take a closer look at the feather structures.