The software appears to be pretty limited when it comes to configuration and features. From what I am seeing, ssOverlay features 2 options, one to choose the level and one to choose the color. There is nothing else regarding advanced customization, therefore it's impossible to say how to obtain different colors and shades.
I've searched on other websites as well, but the same options are available and no tutorial or user guide regarding the way you can customize colors or shades.