ruby shoes convert to hex code from ask_color

I have tried many times to resolve this problem. Please help me.

I created this code:

Shoes.app do
  button "Color" do
    @giv_color=ask_color("Seleziona un colore")
    def rgb(r, g, b)
      "##{to_hex r}#{to_hex g}#{to_hex b}"
    end
    def to_hex(n)
      n.to_s(16).rjust(2, '0').upcase
    end
    para @giv_color # => this give me a result in rgb of a selected color ( es. rgb(20, 20, 40) )
    para rgb(100, 200, 300) #=> this give me a correct hex color convetided
  end
end

I'm not understanding why I am not converting the value rgb in hex code automatically.

I found the solution on its own after several attempts. I did not realize what I was returning from the color selection was a string, clean the latter and converted to integer numbers I have solved the riddle. Thanks for your help.

#!/usr/bin/ruby
Shoes.app do
  button "Color" do
    @giv_color=ask_color("Seleziona un colore")
  def rgb(r, g, b)
      "#{to_hex r}#{to_hex g}#{to_hex b}"
      end
    def to_hex(n)
       n.to_s(16).rjust(2, '0').upcase
end
  arr = @giv_color.inspect.tr('rgb()','').split(',') # clean string returned from selected color
  a = arr[0].to_i #--|
  b = arr[1].to_i #  | ---- convert the string number on integer
  c = arr[2].to_i #--|

  hex = rgb(a, b, c)
  para hex # <<--- return the hex code
  end

end