COLOR_MODEL settings 3 and 4 are similar to models 1 and 2. The primary difference is in reverse-video, which appears as white-on-gray. Also, background colors are brighter.
For COLOR_MODEL 3, the foreground and background colors are exchanged for each other, but only if they are both black or white. If either the foreground or background contains a color other than black or white, nothing happens. This is equivalent to running the monochrome parts of your program in reverse-video while maintaining the color portions unchanged.
For COLOR_MODEL 4, the foreground and background colors are exchanged for each other, but only if the background is black. This mode insures that you never have a black background.
COLOR_MODEL 3 is equivalent to COLOR_TRANS 3, INTENSITY_FLAGS 34.
COLOR_MODEL 4 is equivalent to COLOR_TRANS 1, INTENSITY_FLAGS 34.