While this mode is enabled, the colors of both new and existing rings are inverted. The background color is not affected. Inversion is not the same as rotating the hue 180° (e.g. by doing two Rotate Hue commands), because it's done in RGB space, and therefore flips the lightness as well as the hue. Note that in Invert Color mode, the direction of the Lightness parameter is reversed: increasing it makes the image darker.