Male Ruby-throated Hummingbirds are not seen as often as the females. The bright red feathers on the throats of the males sometimes appears dark or black because they are iridescent. The color depends on the angle of the light.
Here is a close-up of a female at the feeder.
The green feathers on the backs of the Hummingbirds are also iridescent. Sometimes they look green and at other times they may appear to be gray or black.
Thanks to Connie Hardy for taking these Hummingbird pictures.