Hi Akvile and folks,

> as soon as i ad the procedure to my programm my Shoes screen
> turnes black an the colors appear at the same time and not
> differentiated as they should.
Umm,...
I tried out the code you posted with my Shoes 3 (0.r1514) on Windows 7.
But the Shoes screen didn't turn to black...
What platform and Shoes version are you using?
You might have found a bug...

Anyway, try out the following.
I think it's better to use timer() method.

Shoes.app do
  button "P" do
    timer 2 do
      oval :top=> 50, :left=> 150, :radius=> 25, :fill => red
    end
    timer 15 do
      oval :top=> 150, :left=> 150, :radius=> 25, :fill => green
    end
  end
end

And one more shot. ;-)
If you want to change the color of the same light,
try out the following.

Shoes.app do
  nostroke
  light1 = oval :top=> 50, :left=> 150, :radius=> 25
  light2 = oval :top=> 150, :left=> 150, :radius=> 25
  button "P" do
    timer 2 do
      light1.fill = red
    end
    timer 15 do
      light2.fill = green
    end
  end
end

Cheers and have fun Shoes,
ashbb