Problem using 'annotate' toolbar

Hi

I'm new here and also new to the Mac.
I'm having an irritating problem editing a jpg image..
I have been using 'annotate' to place coloured circles and squares around part of a jpg image but somehow I've managed to 'grey' out the colour and line width pop up menus in the toolbar. So now I am unable to use this facility; can anyone please tell me how I can bring these features 'back to life'? Many thanks...