Index of /test/html/parsing/color-attributes/the-algorithm

      Name                    Last modified      Size  Description
      Parent Directory                             -   
      003.htm                 2007-09-17 10:29  189   the empty string (quirks mode)
      004.htm                 2007-09-17 10:29  208   the empty string (standards mode)
      001.htm                 2007-09-17 10:26   12K  HTML color attribute processing tests (quirks mode)
      002.htm                 2007-09-17 10:26   12K  HTML color attribute processing tests (standards mode)

   1. If the string is the empty string, act as if the attribute was
      absent and abort these steps.
   2. If the string ASCII-case-insensitively matches a css3-color keyword
      or one of the CSS2 System Colors, or is "transparent"
      (ASCII-case-insensitively), use that and abort these steps.
   3. Trim all but the first 128 chars from the string.
   4. If it exists, strip the first leading #.
   5. Replace non-valid-hex chars with 0s.
   6. ASCII-lower-case the string.
   7. Make string length a multiple of 3 and a minimum of 3 by appending
      0s.
   8. Split the string into 3 equal segments.
   9. Trim all but the right-most 8 chars from each segment.
  10. If segment length is 1, left-pad each segment with a 0, else:
  11. While segment length is greater than 2 and the first char of each
      segment is equal to 0, trim the left-most char from each segment,
      then:
  12. Trim all but the first 2 chars from each segment.
  13. Join the segments and append them to a # char to create the final
      string.

Also see: https://bugzilla.mozilla.org/attachment.cgi?id=188040