Why the different colours?

Colour coded springs on a cafeteria cart at the Sumerland Health Care Centre

I was at the health care centre in Summerland last week. I saw these springs on the side of a cart holding plastic trays full of mugs.

I wondered why the springs were different colours. My guess is that the colours indicate the diameter and therefore the strength of the springs. Depending on the weight load in the trays the users can adjust the strength of the springs to yield the optimum performance.

Sort of clever as the paint is pretty durable, while some little tag might easily fall off.