The fillColor property define the backcolor for the field object.
System.Array fillColor();
The array for this property uses the color array type:
Transparent: ["T"]
Gray: ["G", #1] where #1 is 0 for black and 1 for white.
RGB ["RGB", #1, #2, #3] where #1 red color 0-255, #2 green color 0-255 and #3 blue color 0-255.
CMYK ["CMYK", #1, #2, #3, #4] where #1 cyan color 0-255, #2 magenta color 0-255, #3 yellow color 0-255 and #4 black color 0-255.
Member of field.