def similarity(color)
      distance({ :r => @red, :g => @green, :b => @blue}, { :r => color.red, :g => color.green, :b => color.blue}) / sqrt(3 * (255 ** 2))
    end
def similarity(color)
      distance({ :r => @red, :g => @green, :b => @blue}, { :r => color.red, :g => color.green, :b => color.blue}) / sqrt(3 * (255 ** 2))
    end
Calculate the similarity between the receiver and another {Color}
 @param [Color] color color to calculate the similarity to
 @return [Number] a value in [0..1] with 0 being identical and 1 being as dissimilar as possible