Point FModel at Palworld
FModel reads the game's packed archives without modifying them. On first launch, add Palworld as an undetected game and point it at Palworld\Pal\Content\Paks; FModel detects the Unreal version itself. You can now browse every texture, model and data table the game ships with.
Find and export the texture
Search for the asset by name — Pal textures follow the game's internal naming, so browsing the Characters folder while filtering by the Pal's name usually lands you on it. Export as PNG (FModel converts from the engine format) and note the full internal path; the replacement must reproduce that path exactly.
Edit and rebuild the tree
Repaint the PNG in any editor, keeping the same dimensions. Then recreate the folder structure from the internal path on disk — your mod folder mirrors the game's content tree, with your edited file sitting where the original sits inside the pak.
Pack with repak and test
Run repak pack on your mod folder to produce a .pak, drop it into Palworld\Pal\Content\Paks\~mods and load a save. If the game shows the old texture, the internal path or filename differs from the original — the pak loaded, but it is overriding nothing. Name the .pak so it sorts after any other mod touching the same asset.