Red tears of sweat stream yellow

Red tears of sweat stream down the yellow-painted face of a Huli wigman in Papua New Guinea. His elaborate costume, donned for a ceremonial welcoming dance called the sing-sing, also includes a dramatic wig of human hair.

Pink flowersyellow

Pink flowers and a hand-painted sign advertising treasures adorn a yellow-and-red building in San Miguel de Allende, Mexico. The city's beauty and mild climate have attracted many foreign residents.

A brightly painted train engineYellow

 brightly painted train engine stands under a deep blue sky in Santa Fe, New Mexico. The Santa Fe Railroad, one of America's most famous, merged with the Burlington Northern Railroad in the mid-1990s.

A time-lapse photo yellow

A time-lapse photo captures the wispy steam and yellow glow of the Georgia-Pacific paper mill in Brunswick, Georgia, at night. The mill is surrounded by the wetlands of poet Sidney Lanier's "Marshes of Glynn."

A staircase standsyellow

A staircase stands in sharp relief against a wall of yellow stained glass at the University of Colorado in Boulder.

Yellow

A yellow boat hull is reflected at the waterline in Quebec’s Forillon National Park. This oceanside park is located at the farthest tip of Gaspe Peninsula.

Life in Color: Yellow

Yellow evokes the shine of the sun and is found throughout nature and the man-made world as a color that commands attention. This highly visible hue is found on everything from bumblebees to school buses, traffic signs to highlighters. Misbehaving soccer players are shown yellow as a warning, and Tour de France racers know the man in yellow is the rider to beat.

Here, a woman in Diafarabe, Mali, holds her brilliant yellow scarf against a deep blue African sky. Her landlocked country is a desert land that was once a hub for ancient Saharan caravan routes.

Life in Color: Purple

Purple is a versatile color. Combining the fire of red with the serenity of blue, it has the ability to soothe as well as excite passion. Purple is prevalent in nature in everything from eggplants to amethysts, and humans have adopted it as a symbol of royalty.

Here, Ross Bridge in Tasmania is cloaked in a mauve sunset. The beautiful sandstone span, built by convicts in 1836, is one of Australia's oldest and is decorated with an impressive array of carvings.

Green

In a nocturnal rendezvous, two green tree frogs meet face-to-face atop a leaf in Louisiana's Atchafalaya River Delta. Green may be the most common color found in nature—it's everywhere from leaves, grass, and moss to snakes, butterflies, and even the northern lights. Green represents life, vitality, nature, and, of course, environmentalism.

Life in Color: Blue

The sweeping color of sea and sky, blue is a common thread in nature, seen in the cerulean of a whale shark (pictured here), the indigo of a stormy night, and the cobalt of a peacock's feathers. Over the centuries, the hue has come to represent calm, cold, mysticism, and sadness.

Underwater Oddities

Ribbons of red nudibranch  eggs curl near Malaysia's Mabul Island. Nudibranchs, also called sea slugs, lay their eggs on the seafloor, attached to coral or rocks. Although a nudibranch is a simultaneous hermaphrodite (possessing both male and female reproductive organs), it reproduces by finding a partner. Millions of eggs can be found in one egg spiral.