Red is the color of the red color spectrum. It does not belong to any subspectrum, or a narrower group within a broader spectrum..
Web specifications of the red color include its representations in various color models. A color model is an abstract, mathematical way of describing any color via a combination of numerical parameters.
Red Green Blue (RGB)
The RGB or Red, Green, Blue color model is a color model that describes any color as a mixture of red, green, and blue colors. This is an additive color model, meaning that it adds different amounts of red, green and blue to black, black being the absence of color. The red color consists of 100% red, 0% green and 0% blue. In absolute RGB units (where the minimum is 0 and the maximum is 255) it is 255 red, 0 green and 0 blue. In other words, the RGB code of the red color is RGB (255, 0, 0)
The HEX or hexadecimal color model is a color model that describes colors with a combination of six or 3 (shortened version when applicable) hexadecimal values, ranging from 0 to 9 and from a (representing 10) to f (representing 15). The six characters are divided into three pairs, where the first two characters represent the color red, the middle two - green, and the last two - blue. Much like the RGB color model HEX describes any color as a combination of red, green and blue with the minimum of 0 (00 in HEX) and the maximum of 255 (ff in HEX). The HEX code of the red color is FF0000.
Cyan, Magenta, Yellow, Key (CMYK)
The CMYK or Cyan, Magenta, Yellow, Key (black) color model is a color model that describes any color as a mixture of cyan, magenta, and yellow colors. Alternative names for the CMYK color model are process color model and four color model. This is a subtractive color model, mainly used in printing, meaning that it subtracts different amounts of cyan, magenta, yellow and black from white, where white is the natural color of paper. The red color consists of 0 percent cyan, 100 percent magenta, 100 percent yellow and 0 percent black. In other words, the CMYK code of the red color is CMYK (0%, 100%, 100%, 0%).
Web safe color
Web safe colors comprise 216 colors that in the past were the only colors guaranteed to be displayed properly on any operating system and any (up-to-date technology-wise) monitor. This palette comes from times when monitors could only display 256 color, and only 216 of them were the same on all the major operating systems. Nowadays, web safe colors are rarely used exclusively, as the abovementioned limitations do not exist anymore. However, if you want to make a website in '90s web design you should know that the red color is one of the web safe colors.