Yes, I understand that RGB to another color model is not linear, but it can be converted back and forth, with a little bit of loss, true. But that is not really the problem here. Let's just forget RGB and work with HSV.
I have a color that has an H, S, and V component. The Hue/Saturation tool allows me to "Add" to the hue and lightness, and adjust saturation (another add I assume, but maybe that is where I am getting goofed up.)
If I want it to add 140 to the hue, 15 to saturation, and 10 to lightness, the result is not my expected H 343, S100, V73, it is something different. I get H 343, S 88, V 88. Why is that?
OK, so I've got the "picture" - so to speak - that this is not what the plugin is supposed to do. So where do I find that "color replacement tool"?
Thanks!
Oh, and I don't want to replace just one color, but many shades of that color. My baseline color makes up about 90% of the image, and is complex enough that I don't want to hand replace all the different shades by hand.