Do Air Force operators wear the "Mustard stains" on their Parachutist badges?

Any info would be appreciated.

If you're referring to the gold star for a combat jump (MFF or SL, or both), yes.

Thanks for responding so quickly!

As to the Combat stars,

Is the wearing of them mandated or a personal preference?

The Bronze Star on a military parachutist badge is a significant battle honor. A person getting such recognition generally doesn’t avoid wearing it. I would also say if bronze star denoting combat jump is awarded, it's mandatory, if the awarded parchutist badge is being worn.

A bronze service star is authorized to be worn on the Parachutist Badges to denote a military member’s participation in a combat parachute jump. Orders are required to confirm award of these badges.

1. The military parachutist must physically exit the aircraft to receive combat parachute jump credit and to be presented award of the Parachutist Badge with bronze service star.

2. The jump must be directly connected to a unit or team performing a jump into an active combat zone.

3. For conventional airborne forces the general criteria is the assault operation is expected to be such that the committed forces will ultimately control the area in which they have landed and not rely on immediate link-up with other forces. Special operation forces have slightly different criteria as they typically are not committed to ultimately control an area.

4. Battle honors means both elements of combat conditions exist: (1) activity against an enemy or opposing force (or activity supporting forces engaging an enemy or opposing force); and (2) risk of exposure to hostile fire. Thus being there means participating in combat operations were military combatants are prepared to give their life in combat and the peril was such that it is expected some of these military combatants will or did give their life in direct combat with the enemy.

5. The standard concisely and clearly states emergency bailout or ejection falls short of the standard needed for award of a bronze star on a parachutist badge.

6. Jump manifest of all jumpers participating in performing the combat jump, the units they are assigned to, the drop zone, and other operational information, such as aircraft tail number, lat/long of DZ, time the jump was made is permanently kept on record. Doesn't matter if it was a conventional combat parachute jump or a highly classified special operations combat parachute jump.

Thank you!

How often do you see this criteria met in Pararescue?

Often enough.