WebGL guru

We are using this WebGL code [login to view URL] on our website's homepage ( [login to view URL] ) The WebGL Scripts includes a CANVAS to show the Letter "N" While hovering the Project Thumb image. And also the CANVAS script changes the PNG image background into black. We also have this functionality in our website to make the whole background white or black ( please see attached ) We are trying to see if we can change the back canvas background white too while so we avoid the black borders?