Purple

Purple is a color that ranges from pale, reddish shades to deeper tones that can approach blue or violet. In everyday language, purple refers to a family of colors rather than one precisely defined point in the visible spectrum. Unlike spectral colors such as green or blue, ordinary purple does not correspond to a single wavelength of light. It is usually perceived when our eyes receive a combination of shorter- and longer-wavelength light, especially blue and red components.

The three main types of cone cells in the retina respond to different ranges of light, and the brain compares their signals to create our experience of color. This means that purple can be produced by different mixtures of light or by materials that reflect different combinations of wavelengths. Its appearance also depends on brightness, illumination, and surrounding colors, so the same purple surface may look different in different conditions. Purple occurs naturally in many flowers, fruits, minerals, and animals.

Plants can produce purple shades with pigments such as anthocyanins, a group of compounds responsible for many red, purple, and blue colors in flowers and other plant tissues. The exact color produced by these pigments can change according to factors such as acidity and the chemical environment. Some animals also appear purple because of pigments or microscopic structures that interact with light. Humans use purple in clothing, art, decoration, printing, signs, and digital design.

On a screen, purple can be created by combining red and blue light at suitable intensities, with the exact balance determining the shade. This is different from mixing physical pigments, which absorb parts of the visible spectrum instead of adding light. Purple therefore provides a useful example of how color depends not only on the properties of light and materials, but also on the way the human visual system interprets the signals reaching the eyes.