The easiest way to start with configuration variables is to try the various COLOR_MODEL settings. If your application is entirely black and white, try all the odd-numbered settings (they affect black and white only), and select the one you like best.
If your program makes use of color, first decide whether or not you like the color portions as they exist in your program. If you do, try the odd-numbered settings to change the black and white portions. If you want to modify your colored portions, try the even-numbered settings.