In the figure, we are looking at the front of the RCU from the astronaut's right.
The Status Indicators are located in four windows in front of the Fan Switch.
They are labeled O2, Pres(sure), Vent,  and H2O. A fifth window, labeled CO2, was never used.
See, also, Section 2.5.7 in the EMU Handbook

Status Indicators (Warning Flags): Any one of four problems
(high oxygen flow, low vent flow, low PGA pressure, or low feedwater pressure)
will cause a cylinder to rotate and reveal an illuminated warning symbol underneath
as indicated in the following table