In practice you have to increase the thresholds for the RGB channels. In a regular image, very few pixels are exactly of a given color, so unless you give some margin very few pixels will be affected by the change.
This said I 've been using Gimp for a while now and I don't remember using color exchange, to there are possibly other/better ways to do what you want. what are you trying to achieve?
This said I 've been using Gimp for a while now and I don't remember using color exchange, to there are possibly other/better ways to do what you want. what are you trying to achieve?