Hey, indexation just try to match the current color with the nearest color of a palette. But if you have a green color you can play with the hue to make it red then it will match the red color of your palette.
But in a future update should be nice to add a matching palette. The matching palette could swap the color by taking the same color index of the main palette.
I already created a subject for this : https://itch.io/t/1137459/palette-swap-feature