Seeing HTML colors
A major feature of HTML and its sister, CSS, is the ability to assign colors and styles to pages. It would seem that the visually impaired might experience some difficulty in “seeing” colors. However, given the nature of HTML colorcodes, the blind and visually impaired can, with some degree of accuracy, describe colors and their placement on web pages by reading the code.
HTML colors are generally assigned values in HTML code by names (Red, Light Coral, etc.), and/or decimal and hexadecimal values, decimal and hexadecimal values being the means by which the VI can perceive colors. This is accomplished by understanding those numeric representations. HTML colors are assigned values based on the colors of red, green and blue, or RGB. Each color has a range on a decimal scale from 0-255 (256 possibilities), 0 being the absence of color (black). Black in a decimal representation would be RGB(0,0,0), or the absence of color while white is RGB(255,255,255). For example, RGB (255, 0, 0, ) would be pure red while RGB (255,100,100) would be a darker red since G (green)and B (blue) values add some gray shading. Hexadecimal (Base 16) is the same except 0-255 is represented in Base 16 with each RGB value represented as as 00-ff. So, in our example, pure red again, would be #ff0000. (The # and RGB are HTML tags for assignment of colors, either hexadecimal or decimal, respectively).
I created a Braille chart from representations on this web page, HTML Color Codes and my students really enjoyed picking colors with exotic names like LightGoldenrodYellow (#FAFAD2, RGB(250, 250, 210)) and applying them to their web pages. The more obvious colors, such as the red, were easy for them to describe and they could guess at more nuanced colors. It is interesting that the higher the values in combination, the lighter the colors and vice versa.
All in all, the students were able to create some very interesting, colorful web pages by understanding how the numeric representations were applied. In my experience, most VI students can perceive light and dark to varying degrees and this helped to understand how colors are formulated. A science teacher could describe light frequencies and wavelengths in conjuction with HTML colors to help student understand the mathematical representations. This page, Color Picker easily demonstrates the concepts above, albeit visually: