Flashes of brilliant iridescence is the dominant characteristics of most hummingbirds. In Placer County the colors that you can expect to see most often are vibrant hues of green, red, orange, and purple. At first glance hummingbirds may all look alike. They are small brownish green , black and white, but when the light hits right they glisten and glitter with metallic color.
These two photos are of the same Anna's Hummingbird taken within 20 seconds of each other. The one on the top was taken without a flash (thus not much light reflecting), the photo on the bottom shows all the brilliant colors that are typical of an Anna's male hummingbird.
Males show the result of sexual dimorphism, they are more iridescently colored than their female counterpart. Their throats and heads have feathers that refract light like a prism, the structure of these feathers cause only certain frequencies of color to be refracted back to the viewer.
When seen through a microscope a hummingbirds iridescent plumage reveals a number of small hollow platelets of melanin, arranged in ridge like layers. It is the thickness and number of layers that affect the wavelengths of color that is reflected. Some layers intensify the color others cancel out color. The color of any particular part of a feather also depends upon the distance between the microscopic ridges in this grid like structure. The resulting colors are much more vivid and iridescent than those of birds with only pigmented feathers.