If you are new to the reformer, the springs look like a difficulty dial. More springs, more resistance, harder class. Fewer springs, less resistance, easier class. That reading is not wrong, but it misses the point. The springs on a reformer bed change which muscle group is asked to do the work, not just how hard that group works.
A heavy spring setting on footwork asks the glutes and quads to push the carriage out. A light spring setting on footwork asks the hamstrings and the deep core to control the carriage coming back in. Both settings look like the same exercise from the outside. They train different things.
In Reformer Foundations we start everyone on a moderate spring setting for footwork — two reds and a blue on most beds — so that the push and the return both have something to work against. In Reformer Flow we drop the springs for the abdominal series so that the carriage is unstable and the core has to hold it. In Reformer Strength we add springs back for the leg work so that the glutes get the load.
The shorthand we teach in Foundations is this: heavy springs for pushing, light springs for stabilising, no springs for control work. By the end of Foundations you should be able to look at the next exercise on the card and know which of those three it is, and set the springs yourself before the coach comes over.
The other thing to know is that spring colour coding varies by manufacturer. Our beds are from the same maker, so the colours are consistent across all three studios. If you have used a reformer at a different studio before, ask the coach in your first class to walk you through the colour-to-resistance map on our beds. It takes two minutes and it saves you from loading the wrong spring for the first three classes.