In the 1990s, most computer screen could display only 256 colors. In many cases, these colors were programmed in the hardware or, at times, could be changed by using a color table. Because of this, if an image had a color which was not included “in the system”, a different (closest) one had to be used or an attempt to produce it would be made through dithering.
The idea of web-safe colors came about when a need for a standard list arose. If one were to take 6 equally spaced shades of the three primary colors of the RGB model, a list of 216 colors would emerge. Additionally, these colors could also be represented by the hex triplet code. This was a huge bonus.
As 256 color displays gave way to 24-bit TrueColor displays, the use of web safe colors gradually decreased and nowadays the list is only for reference. We would never recommend creators sticking to this list and containing their creativity!
Please understand that the web safe colors DO NOT have standard color names. That is a different list with 141 names (with alternate spelling of names removed). The standard color names can be used instead of hex, RGB or HSL values in HTML, CSS and SVG code.