You should ask someone familiar with that particular EDS system. It may be as Jürgen Weippert suggested. Maybe that system flags the currently highlighted element in green. Our Oxford Aztec will normally overlay an elemental profile. I don't know about other systems.
The spectrum is similar to that of orthoclase (KAlSi3O8) or its weathering products. The C is probably that which is virtually ever-present in the SEM. It may be from SEM pump oil or contamination during preparation. Great care is necessary to completely eliminate it. It is only a footnote to the main story.
See if you can get more counts (less noise) next time. Also expand the energy axis to highlight the interesting area. There is nothing going on beyond 5 keV.