Leaves have orange and yellow pigments year-round, but they are masked until the fall, when shorter days reduce the production of chlorophyll, a green pigment.

Egg yolks and carrots have the same pigments that contribute to the yellow and orange colors of fall foliage.

The same pigments that enable photosynthesis—chlorophyll a and b—are also responsible for giving most plants their green color.

Many trees lose their leaves in the fall to conserve resources for future blooming rather than spending them on keeping leaves alive in the wind and cold of winter.

Virtually all plants are biofluorescent because their photosynthesis is powered by chlorophyll, a pigment that glows red as a way to get rid of excess energy when exposed to ultraviolet light.

The chlorophyll in plants captures energy in the form of red and blue light

Breaking down sunlight and why the sun appears yellow despite emitting green light the most

Creating a perfect red pigment that is vivid, durable, and nontoxic is likely impossible.

Violet is the rarest color in nature because it is the most energetically demanding visible light for pigments to reflect and for nanostructures to scatter.

Starting with red, colorful objects will appear to lose their colors the deeper they are submerged because water scatters light, reducing the amount available to reflect off objects and be observed.

Some organisms can change color by quickly revealing or hiding various pigments, as seen in octopuses, squids, and other cephalopods.

Not all colored materials can become pigments—the process of grinding materials down into smaller particles may destroy the color-producing molecules.

'Watermelon snow'—patches of pink, orange, and red in snow—is the result of extremophilic green algae that thrive in extremely frigid conditions and take the shape of red spheres in winter.

Sunsets can exhibit a greater variety of colors due to a greater range of cloud heights and atmospheric composition.

El Niño makes the equatorial Pacific Ocean bluer than usual as high temperatures kill off microscopic plants that normally give the waters a green hue.

View a fall foliage prediction map to estimate the progressive change in the color of leaves throughout the US from September to mid-November.

Blood can be blue, green, magenta, or transparent due to differences in the oxygen-carrying respiratory pigments they contain.

Flamingos get their pink color from pigments in their food, but they cannot be any color because their bodies cannot process every type of pigment.

Imagining if humans could perform photosynthesis and how it would change our anatomy

Bruises go from blue-purple to yellow-green because of a breakdown of hemoglobin—the pigment that carries oxygen throughout the human body.

Reindeers are the only known mammals whose eyes change color with the seasons, going from golden yellow in the summer to deep blue in the winter.

Some octopuses change color while they sleep, potentially in response to dreaming about hiding, hunting, or other activities that involve changing color while awake.

Chameleons change color by altering the spacing of nanocrystals under their skin, which changes what colors of light are absorbed and reflected.

View a gallery of plants made to shine using ultraviolet-induced visible fluorescence photography, in which organisms re-emit the ultraviolet light they are exposed to in vibrant, glowing colors.

Red and green became Christmas colors thanks to holly—and Coca-Cola

The three categories of photosynthesis, which each help plants survive in different environments

The colors of auroras change with the intensity of solar activity and with altitude because of differences in atmospheric density and chemical composition.

Satellites can be used to measure photosynthetic activity worldwide by observing the red, biofluorescent light emitted by chlorophyll in plants.

Cow urine, cuttlefish ink, and burned white lead were among the substances used as pigments throughout history.

Instead of consuming water and carbon dioxide to produce oxygen and sugar, anoxygenic photosynthesis involves alternative reactants and products.

Fertilizers provide essential nutrients to plants for their growth, including nitrogen, phosphorus, and potassium, but an overabundance of these nutrients may also harm plants.

Plants use physical and chemical defenses to protect themselves

Humans can distinguish about 10 million colors—a number that is limited by photopigments that only activate when exposed to specific wavelengths of light.

Some corals absorb harmful ultraviolet radiation and re-emit it as visible light, thereby protecting symbiotic algae within their tissues and providing them with energy for photosynthesis.

This year's first leaf and first bloom in the US, mapped

Blood color differs across the animal kingdom, with some animals producing blood that appears green (a group of lizards in New Guinea) or blue (horseshoe crabs).

Watermelons were once neither red nor sweet

When processing light, the brain can perceive colors with no natural wavelength

Watch a time-lapse of photosynthesis activity across Earth, as seen from space.

Visualize the purpose of stomata in photosynthesis

Red is deeply symbolic in Chinese culture

From the surface, Mars can appear butterscotch, golden brown, and even green

Watch a time-lapse of the 120-day journey of a pumpkin seed growing into an adult fruit.

An overview of oxygenic photosynthesis, which releases oxygen from breaking down water

One theory claims the retinae of SAD patients may fail to adjust to less light in winter

Seasonal allergies don't always show up in childhood

Poison ivy's rash-causing compound is found in the plant's roots, stem, and leaves—so coming into contact with any part of the plant can lead to rashes for the 85% of people who are allergic to it.

Increases in atmospheric carbon dioxide lead plants to produce more pollen

Water is naturally tinted with a slight blue, but sediments and organics can alter its color

Coral reefs get their colors from zooxanthellae—photosynthetic algae that line corals' digestive tracts and provide them with sugars in exchange for a home.

Five things to know about autumnal equinoxes