Open a new rule file, and put this under the line with version:
attr Land_Type = "" # This will connect to your object attribute from the GDB.
Shape --> # This is the start of a rule.
color(getColorByLandUse(Land_Type) # This calls the function below using your attribute.
# Expand this function using your land types, with colors in "hex color" format:
getColorByLandUse(landType) =
case landType == "Residential" : "#ff00ff"
case landType == "Office" : "#0000ff"
else: "#000000"