You can actually comment out the player.colorset properties in DECORATE with no bad side effects in Zandronum, and it should work fine after that if I recall correctly.
That feature is not supported by Zand because Zand has a more flexible system for player colors; Player.ColorSet's only use is to make a set of colors for use in zDoom Multiplayer; Zandronum doesn't understand what those sets are, since it just uses the Red/Green/Blue sliders for player colors.
Even if you did want to use those color sets for something, they would probably be useless since the chex player isn't green, and the engine would likely just recolor the slime that shows on chexter in the pain and death states.
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If you find that it doesn't work with those modifications, feel free to reply again, I'm sure I can get it working in Zand.