Pink color in science and nature

Pink is a pale red color that is named after a flower of the same name. It was first used as a color name in the late 17th century. According to surveys in Europe and the United States, pink is the color most often associated with charm, politeness, sensitivity, tenderness, sweetness, childhood, femininity and the romantic. It is associated with chastity and innocence when combined with white, but associated with eroticism and seduction when combined with purple or black.

Science and nature

Optics
Red is the only color whose lighter shades have a different name, pink, than the color itself. In optics, the word "pink" can refer to any of the pale shades of colors between bluish red to red in hue, of medium to high lightness, and of low to moderate saturation. Although pink is generally considered a tint of red, the hues of most shades of pink are slightly bluish, and lie between red and magenta. A few variations of pink, such as salmon color, lean toward orange.

Why sunrises and sunsets sometimes look pink
As a ray of white sunlight travels through the atmosphere, some of the colors are scattered out of the beam by air molecules and airborne particles. This is called Rayleigh scattering. Colors with a shorter wavelength, such as blue and green, scatter more strongly, and are removed from the light that finally reaches the eye. At sunrise and sunset, when the path of the sunlight through the atmosphere to the eye is longest, the blue and green components are removed almost completely, leaving the longer wavelength orange, red and pink light. The remaining pinkish sunlight can also be scattered by cloud droplets and other relatively large particles, which give the sky above the horizon a pink or reddish glow.

Why cooked beef, cured ham, steamed shrimp and salmon are pink
Raw beef is red, because the muscles of vertebrate animals, such as cows and pigs, contain a protein called myoglobin, which binds oxygen and iron atoms. When beef is cooked, the myoglobin proteins undergo oxidation, and gradually turn from red to pink to brown; that is, from rare to medium to well-done. Pork contains less myoglobin than beef and therefore is less red; when heated, it changes from pinkish-red to less pink to tan or white.

Ham, though it contains myoglobins like beef, undergoes a different transformation. Traditional hams, such as prosciutto, are made by taking the hind leg or thigh of a pig, covering it with sea salt, which removes the moisture content, and then letting it dry or cure for as long as two years. The salt (sodium nitrate) permits the ham to retain its original pink color, even when dried out. Supermarket hams are made by a different and faster process; they are brined, or infused with a salt-water solution, containing sodium nitrite, which transfers nitric oxide, which bonds with the myoglobin to form the traditional pink cured ham color.

The shells and flesh of crustaceans such as crabs, lobsters and shrimp contain a pink carotenoid pigment called astaxanthin. Their shells, naturally blue-green, turn pink or red when cooked. The flesh of the salmon also contains astaxanthins, which makes it pink. Farm-bred salmon are sometimes fed these pigments to improve their pinkness, and it is sometimes also used to enhance the color of egg yolks.

Roast beef gets its distinctive pink color from myoglobin, which gradually turns from red to pink to brown (rare to medium to well-done) when heated.

Prosciutto hams also get their pink color from salt combined with the natural protein called myoglobin.

The shells and flesh of steamed shrimp contain a natural carotenoid pigment called astaxanthin, which turns pink when heated. The same process turns cooked lobster and crab from blue-green to red when they are boiled.

The meat of the salmon is also colored pink by the natural carotenoid pigment called astaxanthin.

Plants and flowers
Pink is one of the most common colors of flowers; it serves to attract the insects and birds necessary for pollination and perhaps also to deter predators. The color comes from natural pigments called anthocyanins, which also provide the pink in raspberries.

A pink rose picture

Pigments - Pinke

In the 17th century, the word pink or pinke was also used to describe a yellowish pigment, which was mixed with blue colors to yield greenish colors. Thomas Jenner's A Book of Drawing, Limning, Washing (1652) categorizes "Pink & blew bice" amongst the greens (p.  38), and specifies several admixtures of greenish colors made with pink—e.g. "Grasse-green is made of Pink and Bice, it is shadowed with Indigo and Pink … French-green of Pink and Indico [shadowed with] Indico" (pp. 38–40). In William Salmon's Polygraphice (1673), "Pink yellow" is mentioned amongst the chief yellow pigments (p. 96), and the reader is instructed to mix it with either Saffron or Ceruse for "sad" or "light" shades thereof, respectively.

Sonics
Pink noise (About this sound sample (help•info)), also known as 1/f noise, in audio engineering is a signal or process with a frequency spectrum such that the power spectral density is proportional to the reciprocal of the frequency.

Lighting
Grow lights often use a combination of red and blue wavelengths, which generally appear pink to the human eye.

Pink neon signs are generally produced using one of two different methods. One method is to use neon gas and a blue or purple phosphor, which generally produces a warmer (more reddish) or more intense shade of pink. Another method is to use an argon/mercury blend and a red phosphor, which generally produces a cooler (more purplish) or softer shade of pink.

Pink LEDs can be produced using two methods, either with a blue LED using two phosphors (yellow for the first phosphor, and red, orange, or pink for the second), or by placing a pink dye on top of a white LED. Color shifting was a common issue with early pink LEDs, where the red, orange, or pink phosphors or dyes faded over time, causing the pink color to eventually shift towards white or blue. These issues have been mitigated by the more recent introduction of more fade-resistant phosphors.

Engineering
Insulation manufactured by Owens Corning is dyed pink, with the Pink Panther as its corporate mascot. The company holds a trademark on the color pink for insulation products in order to prevent competitors from using it, and is the first company in the United States to trademark a color.

The United States Manual on Uniform Traffic Control Devices specifies fluorescent pink as an optional color for traffic signs used for incident management as an alternative to the traditional orange in order to distinguish them from construction zone signs.

Source From Wikipedia