Turns out the NCR up on that mountain were trying to combat radiation sickness. For all their efforts, experimenting on ghouls and super mutants, they've come up with these 'experimental' rad-x pills. The capsules are a single tone of yellowish off-white, not that candy red/yellow of normal rad-x. They're also not safe to take alone, but I found out that mixing them in with a few bottles of irradiated water purifies the water. The soldiers also carry syringes of a kind of sedative or something. It helps. As if I didn't already have enough reasons to take out these guys.