Modifying NPC Sprites

[EnforcerRidley]

I want to make Agahnim red and blue as he is in his artwork, similar to how he is in Redux. So, I'm trying to figure that out how.

This is the latest version of the sprite:

Running the code:
python restool.py --sprites-from-png
results in this error:

I'm assuming that it's because there are other sprites share the same palette (6-7) and they need to match? I can only guess. So far, I see these sprites below also uses palette 6-7:

• StalfosHead
• Lanmolas
• GreenEyegore
• Beamos
• Cannon
• Swamola

Editing them all to have the same edited color scheme seems to result in the same error as above, however.

And palette 5-7 looks to be an identical palette to 6-7:

• Viterous
• ViterousLightning
• Catfish

I've heard the Thief also shares the same palette as Agahnim, but I'm not seeing it in the sheets. I'm seeing a shopkeeper who looks like thief but a different palette.

I should also mention that most of the colors are from the different palettes of Ganon, but some are from the original palette.

What am I doing wrong? Am I going about this the wrong way?