We are attempting to re-skin a third-party application. One modification is to change the background color of a toolbar. However, there are images on the tool bar that have anti-aliased edges to blend into the existing background color. How can I modify those images to blend with a different background color? I only have access to the current image files. I do not have the presumed multi-layer file that was created to do the blending.
Here is the original image. It blends into a light blue background. We want to blend it with a dark blue background.