One way that a "star" can "go out" is if it sets. A bearing of 11:00 o'clock from a heading of 275 deg would be 245 deg. This is close to the azimuth at which the ecliptic cuts the horizon from the location, about 240deg. Planets set here. Venus was setting at mag -2.9 that evening.
The time is given in the telex as MST, in other documents as "Mountain Time" which could be either MST or MDT, but assuming MST is correct 2005 MST converts to 0305 GMT and Venus set at about 0258 GMT from sea level, so at 0305 GMT it was already about 20 arcmin under the horizon. But from 16,000 ft the horizon dip is 1.75arcmin x sqrt4877(m) = 122 arcmin so Venus was 122 - 20 = 102 arcmin = 1.7 deg above the horizon at the start of the sighting and would set in about 10 minutes (these are approximate figures for the area a few miles East of Salton Sea; we don't know precisely where the aircraft was on a minute by minute basis or what the horizon terrain to the west was like).
This is such a close fit to light disappearing that one simnply has to suspect Venus. Colour changes sound like scintilklation, which tends to affect point-source stars much more than planetary discs with sensible angular diameters. But Venus was near its smallest at the time (about 14 arcsec) and colour changes could occur due to refractive turbulence when it was right on the horizon.
The only problematic feature is the motion to the NW. But the report is not very clear. It says the object "_started_ in motion in NW heading and disappeared like turning out a light", implying that this apparent move to the NW was a brief affair. It could have been an illusion. Perhaps plane was turning. A B-50 Superfortress cruising at 244 mph* from Salton Sea on 275 deg for 10 min (chasing the rotation of the Earth and extending the setting time, but not by a great deal) would travel ~40 mi on a heading about 20 deg S of the bearing to March AFB would be placing itself in position to turn _towards the NW_ for an approach to March AFB. The stationary UFO reportedly began to apparently move NW just before it disappeared. This could fit an illusion of "pacing" the plane as it began its turn.
So there's minimal information here, but just enough IMO to suggest that Venus was the likely culprit this time.