I modified a THAW CAS and loaded it in the game. Unfortunately Neversoft has clamped the values to a maximum of 0x5A and 0x4B. I verified this by changing the values, updating the checksum, importing the save file, loading THAW, saving the file in THAW, and re-exporting it again to view in a hex editor. So in short, Neversoft took note of this in THUG2 and didn't want a bunch of flashy messes when people were playing online in THAW.
That doesn't mean the effect itself isn't achievable, if someone would be so kind as to write an infinite colors Gameshark code for THAW I would be able to say for sure if it's possible at all or not. For reference, here is the code for THUG2. It unlocks the saturation and value adjustments.
Inf Sat
207C2D88 00000000
207C2D74 00000000
Inf Val
207C2D88 00000000
207C2D9C 00000000
Someone look into this code please. If we find this effect is possible in THAW that would be pretty amazing.