I think there is still something I'm not successful at conveying. The background color of a notebook tab doesn't exist because it is usually a gradient color going from gray to light gray. So depending on where you draw your SVG it will blend or  won't blend, since you actually need to get the color at the exact pixel where you want to draw the SVG image. 

Why not converting the SVG image to a transparent PNG and then let vision2 draw it  for you? I believe this should work out of the box.