Обратите внимание, когда мы создаем новый образец цвета выбирая цветовую схему Web Safe RGB то подразумеваются совершенно определенные 256 цветов, а на самом деле их только 216 и вот почему

Another set of 216 color values is commonly considered to be the “web-safe” color palette, developed at a time when many computer displays were only capable of displaying 256 colors. A set of colors was needed that could be shown without dithering on 256-color displays; the number 216 was chosen partly because computer operating systems customarily reserved sixteen to twenty colors for their own use; it was also selected because it allows exactly six shades each of red, green, and blue (6 × 6 × 6 = 216).

Мало того, что выбранный мною цвет совсем не web safe, так и еще из этих 216 по-настоящему “безопасных” только 22!

Designers were often encouraged to stick to these 216 “web-safe” colors in their websites; however, 8-bit color displays were much more common when the 216-color palette was developed than they are now. David Lehn and Hadley Stern have since discovered that only 22 of the 216 colors in the web-safe palette are reliably displayed without inconsistent remapping on 16-bit computer displays. They called these 22 colors the “really safe” palette; it consists mainly of shades of green and yellow, as can be seen in the table above, where the “really safe” colors are underlined. [7]

Так что честнее и правильнее было бы назвать эту цветовую модель Web RGB ну уж никак не Web SAFE RGB, так как она позволяет с легкостью задавать цвета весьма далекие от теоретически “безопасных”, а на практике все сводиться всего к 22-м !

источник http://en.wikipedia.org/wiki/Web-safe_color#Web-safe_colors