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Crystal violet or Gentian violet (also hexamethyl pararosaniline chloride) is a triarylmethane dye. The dye is used as a histological stain and in Gram’s method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic properties and was formerly important as a topical antiseptic. The medical use of the dye has been largely superseded by more modern drugs, although it is still listed by the World Health Organization. The name "gentian violet" was originally used for a mixture of methyl pararosaniline dyes (methyl violet) but is now often considered a synonym for crystal violet. The name refers to its colour, being like that of the petals of a gentian flower; it is not made from gentians or from violets.
Color television refers to the technology and practices associated with television’s transmission of moving images in color. In its most basic form, a color broadcast can be created by broadcasting three monochrome images, one each in the three colors of red, green and blue (RGB). When displayed in fast succession, these colors will blend together to produce a single color as seen by the viewer. One of the great technical challenges of introducing color broadcasting was the desire to reduce the high bandwidth, three times that of the existing black-and-white (B&W) standards, into something more acceptable that would not use up most of the available radio spectrum. After considerable research, the NTSC introduced a system that encoded the color information separately from the brightness, and greatly reduced the resolution of the color information in order to conserve bandwidth. The brightness image remained compatible with existing B&W television sets, at slightly reduced resolution, while color televisions could decode the extra information in the signal and produce a limited-color display. The higher resolution B&W and lower resolution color images combine in the eye to produce a seemingly high resolution color image. The NTSC standard represents a major technical achievement. Although introduced in the U.S. in the 1950s, only a few years after black and white televisions had been standardized there, high prices and lack of broadcast material greatly slowed its acceptance in the marketplace. It was not until the late 1960s that color sets started selling in large numbers, due in some part to the introduction of GE’s Porta-Color set in 1966. By the 1970s color sets had become standard, with all-color broadcasts becoming common. Color broadcasting in Europe was not standardized on the PAL format until the 1960s, and broadcasts did not start until 1967. By this point many of the technical problems in the early sets had been worked out, and the spread of color sets in Europe was fairly rapid. Most major markets in North America and Europe were all color by the mid-1970s, and by the 1980s B&W sets had been pushed into niche markets, notably low-power uses, small portable sets, or use as monitor screens in lower-cost consumer equipment and in the television industry. 
Color bars used in a test pattern, sometimes used when no program material is available.
From Wikipedia, the free encyclopedia : Manufacture of coloring matter |
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