I didn't know there was someone working on restoring DKC2, nice!
I colorized DKC. Do not try to find similarities between GBA and SNES palettes. Rare used a custom software to reduce all sprites and backgrounds sizes. And since GBA had more VRAM for palettes, they just didn't worry about keeping the same palettes (as other GBA ports) and let that software create its own palettes. Restoring these palettes is a hell, but it's doable.
What I did was:
* injected these palettes in a level (with a custom tool that allowed me to insert it just by setting an offset):
* opened the game in an emulator, and also the SNES version
* took an screenshot where I could see both GBA/SNES screens and also emulator VRAM palette viewers for both
* used Photoshop, using the eyedropper and paint bucket tools I started to restore every color (using the eyedropper to choose the old color, and the paint bucket to fill its matching GBA color, it would then restore that color in the screen and its emulator VRAM palette viewer color too)
* after restoring all colors, I copied the GBA VRAM palette viewer window and pasted in my custom tool, injecting the whole palette automatically
I still keep a backup of my tool, if you are interested on it. The only edit I'd need is to allow it to decrypt/encrypt LZ77 palettes.