Here is a screengrab from the build doc. Essentially you have two options for a status LED. You can either use a Common Anode Bi-color LED (D1) or use two different color standard LEDs. (DA & DB)
This is purely for aesthetics on how you want your finished pedal to look.
See image below:
This is also referred in the schematic as well by the diode symbols. We suggest looking at schematic even if you are new to them as things will become very familiar, very quickly and that’s always a bonus.