The description of a color by Physicists in terms of its Hue, Saturation, and Brightness dates back to about 1940. Hue values range from 0 to 360 (degrees), and they are often drawn as points on the circumference of a circle. Saturation and Brightness values range from 0 to 100(%). Being based on early analog measurements, all the values can be floating point.
With the advent of color television (and monitors), engineers needed a color description that bore a more direct relationship to the signals sent to the individual red, green and blue color "guns" in a TV tube. The RGB description was the result.
The original RGB description had floating point values ranging from 0 to 100(%). For digital circuits, however, integer values are needed. The current description calls for 256 shades of each color, which range from 0 to 255.
The Applet below contains on the left a choice list of Java's "built- in" colors between examples of the screen color obtained with either this list or with any HSB setting in the middle or any RGB setting on the right. Any changes made in one color description make the corresponding changes in the other and reset the choice list to the top item. For HSB to be anything but black, both Saturation and Brightness must be moved from 0.
The text fields will not allow entries greater than the maximum possible for that value. The scrollbar can be adjusted in three ways: by moving the slider, by clicking for line right or left or for page right or left.