Debut: Not sure what version you are using but your background doesn't necessarily need to be colored green to have this effect working. When you open the Green Screen window, you can select the color of your background and also the threshold to have the flexibility to extend the range of the color you are replacing.
WavePad: The appearance of the program cannot be modified. If you do not like the current version, you may go back and install your previous version. You can search for your previous version here: http://www.oldversiondownload.com/