Please use software that can recognize pallet correctly.
I recommend edge.
(Edge is Japanese software, but I think that there is certainly software that can handle palettes correctly in English.
Basically, most software can not handle pallets well.
Palette is old technology.
In modern times full-color images are commonplace, but in the past you could only use the colors you chose from the palette.
Since GBA is an old machine, pallets are adopted.
I Analyze your image.
This image uses a palette, but the order of the pallet is destroyed.
Looking at your image at the edge will look like this.
It is like this when taking out the original image from the ROM and looking at the edge.
You can see that the order of pallets displayed on the right side is different.
The software you are using can not handle the palette well and destroyed the order of the palettes.
Therefore, originally the 0th color must be the background color, but it is assigned to a different color.
For other colors, the order has become strange.
When importing this image, FEBuilderGBA will apply the color in the order of this palette.
Therefore, the color of the image will be incorrect.
I recommend using software that can use the pallet correctly.