Can't add background on 255 palette image

[MrSaturn100]

So I've been working on a character that has hundreds of random images in its files, but because it's been well over a year since I've had to add anything new to it and I've completely forgotten my method of doing it. What I used to do was go into photoshop and index the images then add the pink background to act as the transparent color, but whenever I try to add the pink to the image I just indexed, it changes the pink to the first color in the color palette and I don't remember how to edit the palette to make the pink go first. I've been stuck on this for hours now and no tutorial is helping me with my problem so I'm at a loss for what to do

To the left in this image is one of the older pictures I used for the character that I was able to complete the process with. To the right is what happens when I do that exact same process but tried to add the pink, only for the color to change


I have no idea what I'm doing wrong and nothing I find online is helping me so I genuinely need help on this..

[xcheatdeath]

shouts to cybaster

https://mugenguild.com/forum/topics/complete-stage-creation-tutorial-104470.0.html

in part 1: "applying a palette" he walks through it there

[Odb718]

As for working with photoshop and similar pages, I just use Fighter Factory 3. It'll work pretty good for you if you know the sprite is 256 colors or less too.
https://mugenguild.com/forum/topics/use-fighter-factory-3-make-palette-fast-177794.0.html
Once you bring your image into your char using FF3, open the palette editor and swap the two colors. Save then force the palette you just saved, and delete the original imported (bad) image.