anchor.diff:    * [`color.hue()`](#hue) for getting a color's hue.
     * [`color.saturation()`](#saturation) for getting a color's saturation.
     * [`color.lightness()`](#lightness) for getting a color's lightness.
  +  * [`color.whiteness()`](#whiteness) for getting a color's whiteness.
  +  * [`color.alpha()`](#alpha) for getting a color's alpha channel.
  +
  +  <% example(autogen_css: false) do %>
  +    @debug color.blackness(#e1d7d2); // 11.7647058824%
  +    @debug color.blackness(white); // 0%
  +    @debug color.blackness(black); // 100%
  +    ===
  +    @debug color.blackness(#e1d7d2)  // 11.7647058824%
  +    @debug color.blackness(white)  // 0%
  +    @debug color.blackness(black)  // 100%
  +  <% end %>
  +<% end %>
  +
  +
  +<% function 'color.blue($color)', 'blue($color)', returns: 'number' do %>
  +  Returns the blue channel of `$color` as a number between 0 and 255.
  +
  +  See also:
  +
  +  * [`color.red()`](#red) for getting a color's red channel.
  +  * [`color.green()`](#green) for getting a color's green channel.
  +  * [`color.hue()`](#hue) for getting a color's hue.
  +  * [`color.saturation()`](#saturation) for getting a color's saturation.
  +  * [`color.lightness()`](#lightness) for getting a color's lightness.
  +  * [`color.whiteness()`](#whiteness) for getting a color's whiteness.
  +  * [`color.blackness()`](#blackness) for getting a color's blackness.
     * [`color.alpha()`](#alpha) for getting a color's alpha channel.
   
     <% example(autogen_css: false) do %>
  
positive.code:   * [`color.blue()`](#blue) for getting a color's blue channel.
    * [`color.saturation()`](#saturation) for getting a color's saturation.
    * [`color.lightness()`](#lightness) for getting a color's lightness.
    * [`color.alpha()`](#alpha) for getting a color's alpha channel.
  
    <% example(autogen_css: false) do %>
  
negative.code:     @debug color.hue(#e1d7d2)  // 20deg
      @debug color.hue(#f2ece4)  // 34.2857142857deg
      @debug color.hue(#dadbdf)  // 228deg
    <% end %>
  <% end %>
  
  
  <% function 'hwb($hue $whiteness $blackness)',
              'hwb($hue $whiteness $blackness / $alpha)',
              'hwb($hue, $whiteness, $blackness, $alpha: 1)', returns: 'color' do %>
    <% impl_status dart: '1.27.0', libsass: false, ruby: false %>
  
    Returns a color with the given [hue, whiteness, and blackness][] and the given
    alpha channel.
  
    [hue, whiteness, and blackness]: https://en.wikipedia.org/wiki/HWB_color_model
  
    The hue is a number between `0deg` and `360deg` (inclusive). The whiteness and
    blackness are numbers between `0%` and `100%` (inclusive). The hue may be
    [unitless][], but the whiteness and blackness must have unit `%`. The alpha
    channel can be specified as either a unitless number between 0 and 1
    (inclusive), or a percentage between `0%` and `100%` (inclusive).
  
    [unitless]: ../values/numbers#units
    
    <% heads_up do %>
      Sass's [special parsing rules][] for slash-separated values make it
      difficult to pass variables for `$blackness` or `$alpha` when using the
      `hwb($hue $whiteness $blackness / $alpha)` signature. Consider using
      `hwb($hue, $whiteness, $blackness, $alpha)` instead.
  
      [special parsing rules]: ../operators/numeric#slash-separated-values
    <% end %>
  
    <% example(autogen_css: false) do %>
      @debug hwb(210, 0%, 60%); // #036
      @debug hwb(34, 89%, 5%); // #f2ece4
      @debug hwb(210 0% 60% / 0.5); // rgba(0, 51, 102, 0.5)
      ===
      @debug hwb(210, 0%, 60%)  // #036
      @debug hwb(34, 89%, 5%)  // #f2ece4
      @debug hwb(210 0% 60% / 0.5)  // rgba(0, 51, 102, 0.5)
    <% end %>
  <% end %>
  
  