Door latch spring color code

Does anyone have a reference for the color coding of the door latch springs of the 1937-38 Plymouth/Dodge car? I've seen one box that was marked Red Heavy Duty which leads me to believe they are of different straight. Is this correct or does the color denote different manufacturers? The ones on my 37 are so strong that I'm afraid I'm going to break the door handles. Thanks, have a great day, and God Bless, Selmer