def colors
      @colors ||= (0...(6 * 7)).map do |n|
        pi_3 = Math::PI / 3
        n *= 1.0 / 6
        r  = (3 * Math.sin(n           ) + 3).to_i
        g  = (3 * Math.sin(n + 2 * pi_3) + 3).to_i
        b  = (3 * Math.sin(n + 4 * pi_3) + 3).to_i
        36 * r + 6 * g + b + 16
      end
    end
def colors
      @colors ||= (0...(6 * 7)).map do |n|
        pi_3 = Math::PI / 3
        n *= 1.0 / 6
        r  = (3 * Math.sin(n           ) + 3).to_i
        g  = (3 * Math.sin(n + 2 * pi_3) + 3).to_i
        b  = (3 * Math.sin(n + 4 * pi_3) + 3).to_i
        36 * r + 6 * g + b + 16
      end
    end
Calculates the colors of the rainbow

 @return [Array]