changeing colour of background

[e deleflie]

Is it possible to change the colour of a background?

I'm trying to animate a background ... like those yellow backgrounds
behind changed fields you see sometimes on web pages .... starts
yellow then fades out.

this code isn't behaving as I'd imagined:

Shoes.app :width => 200, :height => 200, :resizable => false do
  flow :width => 100, :height => 100 do
    @b = background rgb(255, 255, 0)
    animate(24) do |i|
      background rgb(i, i, 0)
      # or ... @b.rgb(i,i,0) ... to avoid creating new background objects?
    end
  end
end

Etienne