You could right click on the shape and 'Export to SVG'. You could then open it in an SVG creator like Inkscape (free) and add a fill to it there. This is basically creating your own SVG then. You may find our Create your own images page useful and also one of our regular customers also has a forum post on tips and settings needed with SVGs to make them draw well in the application.
Okay thanks, I will try this method and if I am still not able to achieve what I want, I will let you know.
I want to add a highlight effect (not the one that highlights the border of a square or triangle) in fact i want to highlight the entire shape, sort of fill it with a light color. Is it possible using Videoscribe?