def nearest_value(css_color)
      value = Value.new(css_color)
      result = @tree.nearest(value.coords)
      result.data if result
    end
def nearest_value(css_color)
      value = Value.new(css_color)
      result = @tree.nearest(value.coords)
      result.data if result
    end
This implements the CIE76 color difference algorithm.
 See http://en.wikipedia.org/wiki/Color_difference#CIE76