In his 1899 speech given after Sir George Stokes read his paper "On the Perception of Colour" at the Victoria Institute, Lord Kelvin casually predicted the future:
Now I spoke of scientific men. There are scientific ladies also—and ladies who are not scientific—and I am sure they will all thoroughly sympathise with scientific men in their appreciation of this beautiful theory.
Sir George Stokes told us that every variety of colour may be produced by the mixture of red, green and violet, and in Maxwell's practical work on the subject of which he spoke, white and black are added in the mixture, white to dilute the intensity of the colour; and black to diminish the total light emitted by a body exposed to sunlight.
Now in these times when ladies are so well occupied with important work that they scarcely have time for shopping, it would be a great comfort to them, if when they wanted a beautiful blue ribbon, they could simply write down on a piece of paper 220.127.116.11.4. and put it in an envelope and send it to the shop; or 18.104.22.168.0 a brilliant yellow, no black in it—3 of red, 4 of green, 0 of violet, 2 of white to brighten it up a little and dilute some of the colour. Do not imagine that you will get green by mixing yellow and blue—on the contrary, you get yellow by mixing red and green, as was first taught by Young, enforced by Helmholtz, and splendidly put in practice by Maxwell.
That's right, Lord Kelvin foresaw the common use of color codes on the Web! Kelvin's idea went even further though, to real world color specification via numerical strings. Unfortunately, the average consumer still can't purchase pretty ribbons or other such things custom dyed from an RGBLK string sent to the shop. (I smell a Web 2.0 business potential...)