OFP script is like a language. The syntax is the grammer of this language. Basically it means that you have to get the spelling and word order right. Whenever you use a command, particularly one that somebody has suggested in the forum, you must[/i][/color] check it in the command ref to make sure that the suggestion is correct and that you understand what's going on. If you don't understand, by all means post again asking for more help. Never blindly accept what anybody - particularly me - writes in the forum.
The colours in this case are just the red, green, or whatever. I always get things like this wrong, hence my comment.
From the comref
group setCombatMode mode
Operand types:
group: Object or Group
mode: String
Type of returned value:
Nothing
Description:
Set group combat mode (engagement rules). Mode may be one of: "BLUE" (Never fire), "GREEN" (Hold fire - defend only), "WHITE" (Hold fire, engage at will), "YELLOW" (Fire at will), "RED" (Fire at will, engage at will).
Example:
groupOne setCombatMode "BLUE".
In this case, I'd suggest starting the AT guns on blue and then switching to yellow. (Rather than red and green.) If you're not sure what the terms like engage at will mean, read the manual that came with CWC.